Mark 9:2-10 (CEB)
Six days later Jesus took Peter, James, and John, and brought them to the top of a very high mountain where they were alone. He was transformed in front of them, and his clothes were amazingly bright, brighter than if they had been bleached white. Elijah and Moses appeared and were talking with Jesus. Peter reacted to all of this by saying to Jesus, “Rabbi, it’s good that we’re here. Let’s make three shrines—one for you, one for Moses, and one for Elijah.” He said this because he didn’t know how to respond, for the three of them were terrified.
Then a cloud overshadowed them, and a voice spoke from the cloud, “This is my Son, whom I dearly love. Listen to him!” Suddenly, looking around, they no longer saw anyone with them except Jesus.
As they were coming down the mountain, he ordered them not to tell anyone what they had seen until after the Human One had risen from the dead. So they kept it to themselves, wondering, “What’s this ‘rising from the dead’?” They asked Jesus, “Why do the legal experts say that Elijah must come first?”
He answered, “Elijah does come first to restore all things. Why was it written that the Human One would suffer many things and be rejected? In fact, I tell you that Elijah has come, but they did to him whatever they wanted, just as it was written about him.”