Mark 9:2-13 NIV
After six days Jesus took Peter, James and John with him and led them up a high mountain, where they were all alone. There he was transfigured before them. His clothes became dazzling white, whiter than anyone in the world could bleach them. And there appeared before them Elijah and Moses, who were talking with Jesus.
Peter said to Jesus, “Rabbi, it is good for us to be here. Let us put up three shelters—one for you, one for Moses and one for Elijah.” (He did not know what to say, they were so frightened.)
Then a cloud appeared and covered them, and a voice came from the cloud: “This is my Son, whom I love. Listen to him!”
Suddenly, when they looked around, they no longer saw anyone with them except Jesus.
As they were coming down the mountain, Jesus gave them orders not to tell anyone what they had seen until the Son of Man had risen from the dead. They kept the matter to themselves, discussing what “rising from the dead” meant.
And they asked him, “Why do the teachers of the law say that Elijah must come first?”
Jesus replied, “To be sure, Elijah does come first, and restores all things. Why then is it written that the Son of Man must suffer much and be rejected? But I tell you, Elijah has come, and they have done to him everything they wished, just as it is written about him.”
NIV: New International Version