One day, Jesus took three of his disciples, Peter, James, and John with him. (This John was not the same person who baptized Jesus.) They went up on a high mountain by themselves.
All of a sudden, Jesus’ face became as bright as the sun and his clothes became as white as light, whiter than anyone on earth could make them.
Then Moses and Elijah, who had both lived hundreds of years earlier, appeared. They talked with Jesus about his death which would soon happen in Jerusalem.
As Moses and Elijah were talking with Jesus, Peter said, “Jesus, it is good for us to be here. Let us make three tents, one for you, one for Moses, and one for Elijah.” Peter did not know what he was saying.
As Peter was talking, a bright cloud came down on top of them and a voice from the cloud said, “This is My Son whom I love. I am pleased with him. Listen to him.” The three disciples were terrified and fell on the ground.
Then Jesus touched them and said, “Do not be afraid. Get up.” When they looked around they saw no one but Jesus

As they went back down the mountain, Jesus said, “Do not tell anyone about what happened here until after I have been raised from the dead.”
note: Moses and Elijah’s sudden disappearance left only Jesus confirming that in Him Old testament prophecy and law were fulfilled. Peter never forgot that moment. In 2Peter.1:16-18 he stated that he was an eyewitness of Christ’s splendour and glory.