What Does 2 Peter 1:17-18 Mean?
16 For we did not follow sophisticated myths when we told you about the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty. 17 For he received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, "This is my Son, whom I love; with him I am well pleased." 18 We ourselves heard this voice that came from heaven when we were with him on the sacred mountain. 
The first word (for) shows that Peter is explaining what he just said. In verse 15, he says he will work to make sure the readers will always be able to remember “these things.” What things? His teaching about the Second coming (which is the dominant topic through the rest of the book). The Apostles were eyewitnesses, not of the Second Coming, but of the majesty of the Second Coming—which proves Jesus’ credibility. Jesus received honor (from God’s words) and glory (from the display of glorious light) at the Transfiguration. “This is my son” is from Psalm 2. The Father is identifying Jesus as the one he spoke to in Psalm 2—the Messiah who will have absolute supremacy and bring about Judgment Day. The fact that Jesus brings the Father pleasure points to Jesus’ intrinsic goodness.

2 Peter 1:16 We did not follow sophisticated myths when we told you about the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty. 17 For he received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, "This is my Son, whom I love; with him I am well pleased." 18 We ourselves heard this voice that came from heaven when we were with him on the sacred mountain. 
The Coming Dawn of the Eternal Day
2 Peter  Part 17
Reliability of Scripture Part 2
2 Peter 1:16-18
    
There is a tractor beam pulling you through life that determines where you will end up. But you have control over what that tractor beam is. Peter reveals the one that will pull you into the wisest and best decisions in life. Discover how a flash of light on an ancient hill can rewrite your future.

Introduction: The Tow Rope of Life
Peter’s Focus: The Second Coming
The Most Important/Certain Future Event
Peter’s Motivation: Make Sure You Don’t Forget
Heart-Forgetfulness
Judgment Day Deniers
Proving the Second Coming
What They Heard
Validation of Jesus
My Son – Psalm 2, the Fearsome King/Judge
Absolute Supremacy
Too Much Wrath?
We Need a King
Plot Twist
Whom I Love (A Good King)
Validation Expressed through Love
Attractive Glory
What They Saw
They Witnessed 2nd Coming Glory
Jesus’ Glory
The Light
1)	Truth
2) Holiness
3) Joy/Life/Salvation
Summary

Introduction: The Tow Rope of Life
The direction of your life is determined by your relationship with ... the future. You always choose what you choose because of what you believe will happen in the future. You drove here tonight because you believed that once you got here, this Bible study would take place. If I decide to eat a brownie, it’s because of what I believe will happen seconds after I put it in my mouth. If you put money in your 401K, it’s because you believe that money will multiply. Whether it’s 1 second in the future or 70 years in the future, your beliefs about the future determine all your decisions in life.
Your assumptions about what will happen function like a rope tow at a ski area, where you just stand up on your skis, grab the rope, and it pulls you up the hill. Your beliefs about the future pull you wherever you’re going in life. It was your beliefs about what your future would be like that pulled you into your current job, your marriage, divorce—beliefs about what’s in the future are why people choose to become Christians, or why they reject Christianity. Beliefs about the future drive all our decisions. And that’s by God’s design. It’s how he wants us to live our lives. Peter makes that point at the end of his book.
2 Peter 3:11 Since [this is going to happen] what kind of people ought you to be? 
You ought to be a certain kind of person because of the future event that Peter was discussing.
Some future events affect your decision-making more than others depending on how important it is to you and how sure you are that it will happen. Some of your beliefs about what will happen in the future affect your decision-making more than they should. Others affect you less than they should. But all of them affect your behavior in proportion to how important they are and how certain they are.
Peter’s Focus: The Second Coming
The Most Important/Certain Future Event
The book of 2 Peter is all about the most certain and most important of all future events—the most important event God ever revealed. This is an event that should drive your decision-making every minute of every day. But for most people in the world, it doesn’t influence any decision they ever make. What is it? The Second Coming of Christ and Judgment Day, which is one of the main features of the Second Coming. If you believe there will be a Judgment Day, and you’re sure of it, and it matters a lot to you, that rope tow will pull you right into a godly, holy life ... unless ... you forget about it. That’s what Peter’s worried about here in ch.1.
Peter’s Motivation: Make Sure You Don’t Forget 
2 Peter 1:15 And I will make every effort to see that after my exodus you will always be able to remember these things. 
What things? The Second Coming. We know that’s what he’s talking about because the very next word is “for” which means “Let me explain.” Then he goes on to talk about the proof of the Second Coming.
2 Peter 1:15 And I will make every effort to see that after my exodus you will always be able to remember these things, 16 for We did not follow ... myths when we told you about the power and coming of our Lord Jesus Christ
Peter says, “I’m worked up about making sure you don’t forget because when we told you about Christ’s Second Coming, we weren’t going by myths. It was verified, substantiated, rock-solid fact.”
Peter devoted his life to making sure we will never forget about the Second Coming and Judgment Day. And you can see that in the rest of the book—he talks about it constantly.
2 Peter 2:3 ... Their condemnation has long been hanging over them, and their destruction has not been sleeping. 4 For if God did not spare angels when they sinned, but sent them to hell,... 5 if he did not spare the ancient world when he brought the flood ... 6 if he condemned the cities of Sodom and Gomorrah by burning them to ashes, and made them an example of what is going to happen to the ungodly ... 9 then the Lord knows how ... to hold the unrighteous for the day of judgment, while continuing their punishment. 
13 They will be paid back with harm for the harm they have done. 
17 ... Blackest darkness is reserved for them. 
Then in Chapter 3 he brings up the flood again because it’s the prototype for the final judgment.
3:5 ... they deliberately forget that long ago ... the world of that time was deluged and destroyed. 7 By the same word the present heavens and earth are reserved for fire, being kept for the day of judgment and destruction of ungodly men. 
10 the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by fire, and the earth and everything in it will be laid bare. ... 12 That day will bring about the destruction of the heavens by fire, and the elements will melt in the heat. 
This whole book is about the judgment that will take place when Jesus comes back.
Heart-Forgetfulness
So in v.15 Peter says, “If it kills me, I’m going to make sure you never forget about Christ’s return.” And you might say, “That’s not an issue for me, Peter. I’m never going to forget.”
It’s true that you probably won’t forget the fact of the Second Coming. But even while your brain remembers the fact, your heart can forget the importance of it, resulting in apathy. And your soul can forget the certainty of it, resulting in doubt. Remember, for a future event to drive your decisions, it has to be important to you and it has to be certain.  So if you have doubts about it or you’re apathetic about it, the Second Coming won’t be that rope tow that pulls you into a godly life.
So I give you that whole, long introduction so you’ll understand the purpose of this paragraph we’re about to study. What Peter wants to do in the rest of chapter 1 is to press the truth of the Second Coming and Judgment Day so deep into your being...  that your mind, soul, spirit, affections, and every other part of you has constant awareness of it...  and total certainty that it’s real...  and profound alertness to how important it is. Peter wants to imprint the Second Coming on every part of your being.
Judgment Day Deniers 
But there’s a problem. Theere are people who will actively try to undermine your confidence that it’s really going to happen.
2 Peter 3:4 [scoffers] will say, "Where is this 'coming' he promised? 
People will mock the idea.
Proving the Second Coming
So Peter knows we’re facing threats from two directions.  From the outside, deceivers trying to undermine our faith. And from the inside, our own hearts, which are prone to apathy and doubt.
So Peter’s got to prove the Second Coming. But how do you do that? It’s one thing to prove an historical event like the crucifixion or Jesus’ resurrection, but how do you prove a future event?
The answer is a little surprising—eyewitness testimony.
2 Peter 1:16 We did not follow sophisticated myths when we told you about the power and coming of our Lord Jesus Christ, but we were eyewitnesses
How could they have eyewitness evidence of the Second Coming? Did they see it? That seems to be what Jesus promised. 
Matthew 16:28 I tell you the truth, some who are standing here will not taste death before they see the Son of Man coming in his kingdom." 
But the Second Coming hasn’t happened yet, so what was it they saw? I’ll read the rest of the passage.
Matthew 16:28 … some who are standing here will not taste death before they see the Son of Man coming in his kingdom." 1 After six days Jesus took with him Peter, James and John ... and led them up a high mountain by themselves. 2 There he was transfigured before them. His face shone like the sun.
All three gospel describe it that same way.  Jesus says, “Some of you won’t die before you see the kingdom of God come with power” and the very next sentence is that days later they witnessed the Transfiguration. 
So was that Jesus’ Second Coming? No. Look closely at what Peter says they witnessed. 
2 Peter 1:16 ... when we told you about the power and coming of our Lord Jesus Christ, we were eyewitnesses of his majesty.
They didn’t witness the Second Coming, but they did witness the majesty of the Second Coming.
And the majesty they witnessed was enough to dispel any doubts. Usually when we want to prove Christianity, we point to Jesus’ resurrection. But Peter never mentions the resurrection in this book (or the cross for that matter). His focus is on the awesome glory of the Second Coming, and the best proof for that is the majesty that Peter, James, and John witnessed on the Mount of Transfiguration.
And not only the majesty they saw, but even more than that, the words they heard.
2 Peter 1:16 …we were eyewitnesses of his majesty.
18 We ourselves heard this voice that came from heaven when we were with him on the sacred mountain. 
Eyewitnesses and earwitnesses—they saw something and heard something. Peter’s main emphasis is on what they heard, so let’s consider that first, then we’ll look at what they saw.
What They Heard
Validation of Jesus
What did they hear?
2 Peter 1:17 For he received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, "This is my Son, whom I love; with him I am well pleased." 
That’s what they heard—God the Father, speaking from heaven, giving Jesus glory and honor. The glory is mostly in what they saw—we’ll look at that in a minute. The honor is in what God said validating Jesus as his beloved Son with whom God was thoroughly pleased.
Remember, the skeptics are saying, “Where is this ‘coming’ he promised?” The coming who promised? Jesus.
Matthew 16:27 For the Son of Man is going to come in his Father's glory with his angels, and then he will reward each person according to what he has done.
That’s what Jesus promised. How do we know for sure we can believe it? God the Father vouched for him. He gave Jesus honor by giving his stamp of approval on Jesus’ ministry and on his words and co-signing all Jesus’ promises.
My Son – Psalm 2, the Fearsome King/Judge
But God did more than just vouch for Jesus. He says, “This is my Son.” That’s from Psalm 2. God is quoting himself.
Psalm 2:7 ... "You are my Son”
That’s where the whole concept of the Son of God comes from, when the Father calls the Messiah his Son. So at the Transfiguration, God was making a very clear statement that Jesus is the one he was talking to in Psalm 2.”
So what is Psalm 2 about? Well, it’s really about the original “no kings” rally. God installs the Messiah as King in v.6.
Psalm 2:6 "I have installed my King ... on my sacred mountain.”
The Messiah is King, but the psalm describes all of human history as one, giant no kings protest.
Psalm 2:1 Why do the nations conspire and the peoples plot in vain? 2 ... the rulers gather together against the Lord and against his Messiah. 3 "Let us break their chains," they say, "and throw off their fetters." 
“We don’t want to be subject to a king. We’re going to break free!”
But look what the Father says to his Son:
Psalm 2:8 Ask of me, and I will make the nations your inheritance, the ends of the earth your possession. 
Absolute Supremacy
Like it or not, Jesus is the King over everyone everywhere. He not only reigns over them, he owns them.
Remember back in v.11 when Peter said our goal is entry into the eternal kingdom of Christ? That phrase, “eternal kingdom” is taken from Daniel 7:14 where the Son of man is given authority, glory and sovereign power; all peoples, nations and men of every language will worship him.  His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed.  In the Transfiguration, God verified that Jesus was that Son of man.
John 13:3 ... the Father put all things under [Jesus’] power
Ephesians 1:22 And God placed all things under his feet and appointed him to be head over everything
When Jesus comes back, he will have absolute supremacy.
And the rest of Psalm 2 is God warning the rebellious world about the fearsome, terrifying wrath of his Messiah-King.
Psalm 2:9 You will rule them with an iron scepter.
What does it look like for Jesus to rule with an iron scepter? 
9 ... you will dash them to pieces like pottery." 10 Therefore, you kings, be wise; be warned, you rulers of the earth. 11 Serve the Lord with fear ... 12 Kiss the Son, lest he be angry and you be destroyed in your way, for his wrath can flare up in a moment. 
Psalm 2 is about Judgment Day when all of rebellious humanity will find themselves on the business end of the Messiah’s iron scepter.
Revelation 19:15 Out of his mouth comes a sharp sword with which to strike down the nations. "He will rule them with an iron scepter." He treads the winepress of the fury of the wrath of God Almighty.
When Judgment Day comes, the Lamb of God will unleash wrath that has never been seen ever.
Revelation 6:15 Then the kings ... the generals, the rich, the mighty, and every slave and every free man hid in caves ... 16 They called to the mountains and the rocks, "Fall on us and hide us from the face of him who sits on the throne and from the wrath of the Lamb! 17 For the great day of their wrath has come, and who can stand?"
Judgment Day will be a bloodbath because of the wrath of Jesus Christ.
Too Much Wrath?
Most preachers in our culture would get fired if they preached like that. People say, “That’s too much wrath!” People read about hell and they say, “It’s too much punishment—too long, too harsh.”
Is it? When people say hell is too much, God's wrath is too extreme, my question is, "How much injustice is there that needs to be set right?" If Jesus is going to return in power and make all things right, how big a job is that? Think of the most powerful, effective President we’ve ever had. What percentage of evil in the world did he eliminate?  More than 1%? Probably not.
How much evil is there in this world? And given that, what's the right amount of justice? What would you expect an almighty, infinitely holy God to do—bring just a little bit of justice? Or a lot? What's the right amount?
And who is the best person to answer that question... —someone with infinite, perfect knowledge and absolute flawless holiness, or one of the humans contributing to all the evil and injustice, like me?
We don’t have to apologize or downplay or be embarrassed about God’s wrath. If you love justice, then you rejoice at the idea of God bringing it about and eradicating evil, and you trust him to do it in exactly the right way.
And on top of that, we love Judgment Day because for us, that’s the day of reward. That’s why the saints burst out in praise when they consider Judgment Day.
Revelation 11:17 We give thanks to you, Lord God Almighty ... because you have taken your great power and have begun to reign. 18 The nations were angry; and your wrath has come. The time has come for judging the dead, and for rewarding ... your saints ... both small and great-- and for destroying those who destroy the earth.
That’s part of the majesty of our great, just, holy God. And Jesus is the one who will carry it all out.
John 5:22 The Father ... has entrusted all judgment to the Son.
We Need a King
They called those rallies last month “no kings” protests because they wanted a name that everyone would agree with. We fought a revolution against monarchy because we hate the idea of a king. No kings! We hate kings.
But if we hate kings so much, why do we keep creating them? Why do we keep elevating men to positions of high power and honor and authority? We rejected monarchy as a form of government because kings have too much power, but then what have we done since then over the last 250 years? We have consistently voted to give more and more and more power to the government. 
And not just government. If someone can sing or act or play sports, we roll out literal red carpets and elevate them to the highest echelons of society and treat them like royalty. We treat experts like prophets and we base our lives on their writings and proclamations.  We give judges the power to lock us up for life and we give them lifetime appointments with no accountability.
If we're so against kings, why do we do all that? Because as much as we hate kings, we need a king. We need protection, we need justice, we need someone who can organize the culture in a way to bring prosperity, and we need guidance. We’re so desperate for guidance, we’ll elevate morons to be our guides. If the sports celebrity king who can hardly string three sentences together tells us, "Buy these sneakers," we obey. We say, “This guy is a famous actor” (which means he’s really good at pretending), “so let’s put him on TV and ask his opinion about foreign policy or economics or public health.” 
We hate kings, but we can’t help ourselves—we keep on crowning them because as much as we hate kings, we need a king.
Plot Twist
There’s one phrase in Psalm 2 I left out—the very last line of the psalm. And it’s a massive plot twist. By the time you get to the end of Psalm 2, you’re thinking, “Wow, this Son of God, Messiah/King is terrifying. No wonder all of humanity is trying to throw off his rule. I need to get as far away from him as possible.”
But then comes the mother of all plot twists.
Psalm 2:12 Kiss the Son, lest he be angry and you be destroyed in your way, for his wrath can flare up in a moment. Blessed are all who take refuge in him.
You'd think after all that terrifying language about how dangerous he is, the last line would be, "Blessed are those who escape his kingdom." “Blessed are those who find refuge from him.” Take refuge in him? That’s a twist. After going a hundred miles an hour in the negative direction, he throws us for a huge loop when the very last line is in the positive direction.
That might seem out of place at first glance, but if you think about it a little bit, it actually makes perfect sense. His awesome power gives rebels a lot to be afraid of. But if he’s that powerful, imagine if he’s on your side. If he’s my judge, then the stronger he is, the more trouble I’m in. But if he becomes my refuge, then the stronger he is, the safer I am. That’s why we rejoice in the Second Coming.
Monarchy is a bad form of government because if you give that much power to one man, it’s only a matter of time before he goes bad. But what if you had a king who never went bad? A king with ultimate power who was perfectly good who could be your eternal refuge?
Whom I Love (A Good King)
Back to 2 Peter. God quotes himself, but then he adds something that he didn’t say back in Psalm 2.
2 Peter 1:17 ... "This is my Son (that’s from Psalm 2, but then he adds this:), whom I love; with him I am well pleased." 
So God loves Jesus, but doesn’t he love everyone? Not like he loves Jesus. He loves humanity because he created them, but he didn’t create Jesus. He loves believers as his children, but only because of our association with Christ. That’s what it means when it says he loves us in Christ.  But Jesus is the only one he loves simply because he deserves it, because of his intrinsic worthiness.
Validation Expressed through Love
And God not only loves him, but he adds, “in whom I am well-pleased.” Jesus brings him immense pleasure. Watching Jesus, listening to Jesus, interacting with him—everything about Jesus makes God the Father happy—fills him with delight.
What does it take to fill an infinite being with pleasure? Suppose Elon Musk were coming to your house. Richest man in the world, anything he wants to do, he can just do it. And it’s your job to do something special for him to really make him happy. What would you do? How do you impress a billionaire? 
But what if it’s not a billionaire—what if it’s almighty God? How spectacular would something have to be to impress him? He really has seen everything—literally everything.  So what would it take to impress him?
If you showed him some fireworks, would God say, “Wow! I’m in awe!” No. It’s hard to imagine anything that could impress God. And yet when he looks at Jesus, he’s stunned and filled with happiness and has been for all of eternity past—it never got old. How glorious must Jesus Christ be to bring delight into the heart of God? If Jesus Christ is that glorious, and that amazing, and that beautiful and good, and that delightful to stir up even the heart of God the Father, then what would happen in your little heart if you saw even a fraction of his glory? If we looked at him and saw what the Father was seeing that day when he spoke from heaven about how much pleasure he had in Jesus, we would feel more pleasure than we have ever imagined.
Attractive Glory
And just as a quick aside before we go on to what the Apostles saw—this whole principle of Jesus’ worthiness to be loved is a way of presenting the gospel that is too often neglected. Why should you follow Jesus? To avoid wrath on Judgment Day? Yes. To get your sins forgiven and enjoy eternal reward? Sure. Because you were made for holiness and righteousness and Jesus is the way to that? Yes. Lots of reasons to follow Christ. But how about this one: you should love Jesus for the same reason God the Father loves him—just because he is so good.
When you share the gospel with someone, you can talk about the logic of how your sins deserved punishment and Jesus paid that price in your place and all that. But it’s just as important to simply show people how beautiful Jesus is. Just talk about his holiness, wisdom, kindness, perfection—what it’s like when you have an encounter with his presence.  People are moved far more by that which is attractive than by that which is logical. Show people the glory of Christ. That’s what Peter is doing in this book, and it’s what God the Father was doing on the Mount of Transfiguration.
Okay, so now that we’ve looked at what they heard, let’s take a look at what they saw.
What They Saw
They Witnessed 2nd Coming Glory
2 Peter 1:16 ... we were eyewitnesses of his majesty. 
That word majesty means splendor, grandeur, or magnificence. And in the NT it’s only used of deity. Peter says, “We didn’t follow myths when we told you about his powerful Second Coming, but we were eyewitnesses of the magnificence and the divine glory that will be displayed in Christ when he returns.”
And that’s the same staggering, glorious magnificence that will be so overwhelming that it will destroy the Antichrist. Did you know that’s how the Antichrist finally goes down—just by being exposed to Christ’s awesome majesty?
2 Thessalonians 2:8 And then the lawless one will be revealed, whom the Lord Jesus will overthrow ... and destroy by the splendor of his coming.
The majesty and splendor of Christ’s coming will be so awesome and powerful that it will shatter the antichrist. It will be too bright, too awesome, too glorious, too powerful for the antichrist to survive, and it will kill him. And it’s that glorious majesty that Peter, James, and John saw that day on the mountain.
Jesus’ Glory 
And it’s all about light. One thing all the accounts of the Transfiguration have in common is the emphasis on the bright, blinding light radiating from Christ. His face as bright as the sun, his clothes lit up from the inside and flashing like lightning. You can all think back to a time when you saw a flash of lightning.  Can you imagine a person flashing like lightning?  Jesus was emanating spectacular, supernatural, brilliant light.
And it came from inside Jesus.  The terminology that’s used hyperlinks back to when Moses went up on the mountain to meet with God. When that happened, Moses came down with his face glowing, reflecting the glory of God that he had seen. Eventually that wore off because it wasn’t coming from Moses—it was just a reflection. Jesus goes up a mountain and meets with God following the same pattern as Moses, but in Jesus’ case, instead of reflecting glory, Jesus is the source of the glory. It shines out from him through his clothes.
The Light
Why all the light? If God is trying to prove that the promises of the Second Coming are real and are literal, not just symbolic, he’s got to give a display that’s clearly supernatural. He’s asking us to believe in the most supernatural event of all time in the Second Coming, God never asks us to believe without evidence, so to prove it he had to do something miraculous with multiple witnesses.
So you have the supernatural display of light, but it wasn’t just supernatural. There’s a lot of things Jesus could have done to show supernatural power. The point of the Transfiguration was specifically supernatural light. That’s always how it is when God appears visibly to someone in Scripture.  Why?  What does light represent in the Bible?
1)	Truth 
The most common significance is that light either represents or exposes truth. Light reveals reality. If you want to know the truth about what’s in a dark room, you ... flip on the light. Now you know. To have light is to know; lack of light is ignorance. 
John 12:35 ... The man who walks in the dark does not know where he is going.
Our sinful condition has placed us in a realm of darkness, which means we don’t have access to the real world. Until God brings us out of the darkness into the light, we have no way of knowing what’s out there in the spiritual realm. We can only guess, and we have no way of checking the accuracy of our guesses.
People can study the physical world and how it works, but they can’t discover what it’s for. They don’t know why anything exists, including themselves. They don’t know what would make their life a success or failure. They’re in the dark.
Now, as believers, we have some light, but we’re still living in a dark world.
2 Peter 1:19 And we have the word of the prophets made more certain, and you will do well to pay attention to it, as to a light shining in a dark place, until the day dawns 
The Scriptures are like a light in a dark place. It’s the middle of the night, it’s pitch dark, and the Bible is like a flashlight. Flashlights are super helpful when it’s pitch dark for sure, but it’s still nothing like daytime. It’s just a temporary solution to get you by until the sun comes up. Even the Apostle Paul, who had more spiritual insight than anyone, said this:
1 Corinthians 13:12 Now we see but a poor reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully
When will we see face to face and know fully? When the daylight of eternity finally dawns. And who’s going to make that happen? Jesus. That’s the meaning of the light at the Transfiguration.  When Jesus appeared with his face shining like the sun, as a sample of what the Second Coming will be like, it was to show that the coming of Jesus will be the sunrise of that eternal day. For the first time in human history, ignorance, murkiness, confusion, deception, and blindness will all go away. Jesus is the source of all knowledge, he is the means of all perception, all clarity, all truth, and all ability to interact with the real world. He is the daylight.
2) Holiness
And the reason Jesus will expose truth isn’t to make us intellectual; it’s to make us holy. The more clearly you see God, the more you will share in the divine nature. That’s why Peter said back in v.9 that when people don’t exhibit the qualities of God’s nature in their character—when they lack holiness, it’s because they’re blind. So light represents not only truth, but also moral goodness. Light and goodness are used interchangeably. 
Isaiah 5:20 Woe to those who call evil good and good evil, who put darkness for light and light for darkness
Two ways of saying the same thing. When Jesus exploded with light on the Mount of Transfiguration, it illustrated his moral perfection.
And one reason light is such a good illustration of God’s moral character is that light never stays put. There’s no such thing as stationary light. It always radiates out from its source. If you have a dark room and a room that’s brightly lit, and you open a door between the two rooms, the darkness doesn’t shine into the lighted room. Light always dispels darkness.
Jesus radiated light on the mountain to show us that he’s the one who will eliminate not only the darkness of ignorance, but the darkness of evil. When Revelation 21:25 says there will be no night in the New Jerusalem and it won’t need a sun, don’t miss the symbolism. The point isn’t that God will replace the function of the sun in our solar system. It’s a symbolic way of saying moral darkness will no longer exist. All of creation will be flooded with the glorious beauty of God’s perfect goodness.
How is that going to happen? You look at how much evil there is in the world now, how do we get from where we are now to that? Answer: Jesus. That’s the meaning of all that brightness and light at the Transfiguration. 
3) Joy/Life/Salvation
So light represents truth and holiness. It also represents several other wonderful things. Sometimes it’s a synonym for joy.
Psalm 97:11 Light is shed upon the righteous and joy on the upright in heart.
So light and joy go together.
Light also stands for healing (Isa.58:8) and salvation (Ps.27:1) and life (Ps.36:9). To come out of darkness into the light means to receive everything good. When Jesus appeared on the mountain as a source of divine, glorious, blinding light, he was showing that he will be the spring out of which will flow eternal life and salvation and joy and every other good thing in the new heavens and new earth. No wonder the Father takes so much delight in him! Conclusion: Set Your Heart on His Appearing
I’ll end the way I started. The direction of your life is determined by your relationship with the future. We all regret bad decisions we’ve made in the past, and we all want to learn how to make really good decisions now. The biggest key to being a person who makes wise decisions time after time is to set your heart on the Second Coming of Christ, and put all your hope in that day when he arrives, justice is done, everything is made right. Do that, and your decisions will be a rope tow that will pull you up the mountain of a godly life and...  right into the eternal kingdom of our Lord and Savior, the glorious, splendorous, almighty King Jesus when he returns.

Summary
Peter wants to imprint certainty and wonder on our hearts regarding the Second Coming/Judgment Day, so he affirms the truth and literalness of the Transfiguration which points us to Psalm 2. Jesus is the one God spoke to in that Psalm and gave him ultimate supremacy. The light of the Transfiguration shows that Jesus is the one who will bring the dawn of the eternal day (no more ignorance, sin, evil, sorrow, sickness, death, etc.).