Matthew 17:10-13

10And [his] disciples demanded of him saying, Why then say the scribes that Elias must first have come?

11And he answering said to them, Elias indeed comes first and will restore all things.

12But I say unto you that Elias has already come, and they have not known him, but have done unto him whatever they would. Thus also the Son of man is about to suffer from them.

13Then the disciples understood that he spoke to them of John the baptist.