Matthew 17:10-13

And his disciples questioned him, saying, ‘Why then do the scribes say that Elijah it behoveth to come first?’ And Jesus answering said to them, ‘Elijah doth indeed come first, and shall restore all things, and I say to you — Elijah did already come, and they did not know him, but did with him whatever they would, so also the Son of Man is about to suffer by them.’ Then understood the disciples that concerning John the Baptist he spake to them.