Now Peter and those who were with him were heavy with sleep, but when they became fully awake they saw his glory and the two men who stood with him.  And as the men were parting from him, Peter said to Jesus, “Master, it is good that we are here. Let us make three tents, one for you and one for Moses and one for Elijah”— not knowing what he said. [Luke 9:32-33 ESV]
And Peter said to Jesus, “Lord, it is good that we are here. If you wish, I will make three tents here, one for you and one for Moses and one for Elijah.” [Matthew 17:4 ESV]
Peter was practical, his thinking and acting focused completely on his immediate involvement in life. From acquiescing to Jesus command to let down his nets for a catch after a full night of futile work (“Master, we toiled all night and took nothing! But at your word I will let down the nets” [Luke 5:5 ESV]) to his walking on water.
“Lord, if it is you, command me to come to you on the water.” He said, “Come.” So Peter got out of the boat and walked on the water and came to Jesus. But when he saw the wind, he was afraid, and beginning to sink he cried out, “Lord, save me.” [Matthew 14:28-30 ESV]
Peter’s only drawback was his inability to think beyond himself as the center of the world. It is a problem we all share.
While Pete’s life was full, he walked with and was taught by Jesus and after the ascension he traveled the world as the apostle to the Jews, I want to look at the mercy God showed him. Mercy is active love and God showed His active love toward Peter and the other disciples in ways far beyond their limited comprehension.
On the mount of transfiguration Peter came into the presence of God. As you look back in Scripture you will find only two instances where God “showed His glory” to a man. Both times on a mountain, the Mountain of God. Both times shielding those He showed His glory from seeing His face.
When Moses went to God to make the second set of tablets God passed by and shielded him with His hand.
Behold, there is a place by me where you shall stand on the rock, and while my glory passes by I will put you in a cleft of the rock, and I will cover you with my hand until I have passed by. Then I will take away my hand, and you shall see my back, but my face shall not be seen. [Exodus 33:21-23 ESV]
Then, when Elijah ran to God after killing the prophets of Baal and was threatened by Jezebel, he pulled his cloak over his head shielding his face from seeing God.
And he said, “Go out and stand on the mount before the Lord.” And behold, the Lord passed by, and a great and strong wind tore the mountains and broke in pieces the rocks before the Lord, but the Lord was not in the wind. And after the wind an earthquake, but the Lord was not in the earthquake.  And after the earthquake a fire, but the Lord was not in the fire. And after the fire the sound of a low whisper.  And when Elijah heard it, he wrapped his face in his cloak and went out and stood at the entrance of the cave. [1 Kings 19:11-13 ESV]
Are there any other instances in Scripture where sinful man was exposed to the glory of God? Adam and Eve before the fall? Joshua, who never left the tent of meeting while the glory of God was on it? Hananiah, Mishael, and Azariah (Shadrach, Meshach, and Abednego) walking around in the fiery furnace with one who looked like a “son of the gods” [Daniel 3:25 ESV]? How about those who were given visions of God on His throne? None of these were shielded from what they saw yet all saw God. Better, all saw the preincarnate Christ, God the Son.
When Jesus was transformed (metamorphoo) before Peter, James and John, He was transfigured into that which He is truly. Peter, James and John saw Jesus with Moses and Elijah, the only three men who had ever seen God the Father’s glory. What the three disciples saw was Christ in His glory. We make the assumption this was the only time during Christ earthly life where He was transfigured, clothed with His true glory. Yet, Christ went alone many times, as was His habit, up mountains to pray. Just because we are told of one time does not mean He was transfigured only this one time. We have no witnesses of the other times He was alone and there is no reason to believe He was not transfigured at those times, also.
Why Peter said what he did is a mystery. We can make assumptions, something we do willingly as we focus upon ourselves and try to understand a man who walked with Christ. That he and the others saw Christ in His glory is an act of love extended to few in this world. Not until we reach eternity will we see Christ in His glory. Peter, James and John saw Him while living in sinful, rebellious bodies.
There was nothing about these men which qualified them for such an honor. Peter was a sinful man who viewed the world revolving about himself, who wanted things his way. He acknowledged the sinfulness of his heart. He suffered the gentle stinging rebukes of Jesus because of his lack of faith. He denied Christ. By the end of his life he did not see himself worthy to even die the same way Christ died. Throughout, he received God’s gracious mercy even when he did not recognize it.
Mercy is more than God’s actions toward those in pitiable circumstances. Mercy defines God’s actions toward us all the time.