Matthew 17:10-13

And his disciples asked him, saying, Why then say the scribes that Elijah must first come? And he answered and said, Elijah indeed cometh, and shall restore all things: but I say unto you, that Elijah is come already, and they knew him not, but did unto him whatsoever they would. Even so shall the Son of man also suffer of them. Then understood the disciples that he spake unto them of John the Baptist.