Luke 9

"As He prayed, the appearance of His face was altered, and His robe became white and glistening.  And behold, two men talked with Him, who were Moses and Elijah,  who appeared in glory and spoke of His decease which He was about to accomplish at Jerusalem. But Peter and those with him were heavy with sleep; and when they were fully awake, they saw His glory and the two men who stood with Him. Then it happened, as they were parting from Him, that Peter said to Jesus, “Master, it is good for us to be here; and let us make three tabernacles: one for You, one for Moses, and one for Elijah”—not knowing what he said." vv.29-33

Read chapter 9
The Transfiguration.  What an honor for Peter, James and John to be a part of this moment.  I always wonder how they knew it was Moses and Elijah with Jesus?  I mean they didn't have photographs then so even though they would know of them they wouldn't know what they looked like; and I don't think they were wearing name tags, probably just called each other by name and picked up on it.  
It's hard to know what exactly Jesus face looked like when it says it was altered, perhaps from Revelation 1:14-15 we can guess what it might have been like: "His head and hair were white like wool, as white as snow, and His eyes like a flame of fire;  His feet were like fine brass, as if refined in a furnace, and His voice as the sound of many waters."
Now what exactly is happening here is debated.  Some say they are disembodied souls, some say this is a special resurrection of Moses (since Elijah didn't die) and some say this is a vision of the future when Jesus is standing with Moses and Elijah recounting the time leading up to His decease.  I believe with the latter and gather this from many details in scripture.
Lastly we see Peter tell Jesus he wants to building three tabernacles for Jesus, Moses and Elijah.  Why does it seem wrong or out of place?  Well first scripture says he didn't know what he said.  Second, he is putting Jesus on the same plane as Moses and Elijah.  Third, Peter seems to act rashly not knowing what to say but thinking he needs to say something to try to prolong the moment.  How sometimes do we respond like Peter to great things of the Lord by saying or doing something just to put in our two cents or feel like we have to add to it then just soak the moment in?