Mark 9:11-12

11 Then the three disciples asked Jesus, ‘Why do the teachers of God's Law say that God's prophet Elijah must return first, before the Messiah comes?’

12 Jesus said to them, ‘Elijah does come first. He makes everything ready. But what is written in the Bible about the Son of Man? It says that people will cause him to suffer a lot. They will think that he is nothing.