Jesus told them that the one like Elijah has already come and been evilly treated, but that the Messiah would also be evilly treated.

Mark 9:9-13

9 While they were coming down the mountain, Jesus told them that they should not tell anyone yet what had just happened to him. He said, “You may tell them after I, the one who came from heaven, ◄rise from the dead/become alive again► after I die.” 10 So they did not tell others about it for a long time. But they discussed among themselves what it meant when he said that he would ◄rise from the dead/become alive again► after he died.

11 The three disciples had just seen Elijah, but Elijah had not done anything to prepare people to accept Jesus. So they asked Jesus, “The men who teach the Jewish laws say that Elijah must come back to the earth before the Messiah comes to earth. But you have been here a long time and Elijah came just today. So is what they are teaching wrong?” 12-13 12-13Jesus wanted them to know that John the Baptizer was the one who represented Elijah. So he answered them, “It is true that God promised to send Elijah to come first so that people would be ready when I came. Elijah’s representative has already come, and our leaders treated him very badly, just like they wanted to do, just like it was prophesied {the prophets prophesied} long ago. But, ◄I also want you to consider what is written {what the prophets wrote} in the Scriptures about me, the one who came from heaven./why have you not thought about what is written {what the prophets wrote} about me, the one who came from heaven?► [RHQ] It is written {They wrote} that I would suffer much and that I would be rejected {that many people would reject me}.”