Matthew 17:10-13

10And the disciples asked him, "Then why do the scribes say that first Elijah must come?"

11He answered, "Elijah does come, and he will restore all things.

12But I tell you that Elijah has already come, and they did not recognize him, but did to him whatever they pleased. So also the Son of Man will certainly suffer at their hands."

13Then the disciples understood that he was speaking to them of John the Baptist.