John Chrysostom
Catena Aurea · Matthäusevangelium 17
And his disciples asked him, saying, Why then say the Scribes that Elias must first come? And Jesus answered and said unto them, Elias truly shall first come, and restore all things. But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them. Then the disciples understood that he spake unto them of John the Baptist.
But if there shall so much good arise out of the presence of Elias, why did He not send him at that time? We shall say, Because they then held Christ to be Elias, and yet believed not on Him. But they shall hereafter believe Elias, because when he shall come after so great expectation announcing Jesus, they will more readily receive what shall be taught by Him. But when He says that Elias is come already, He calls John the Baptist Elias from the resemblance of their ministry; for as Elias shall be the forerunner of His second coming, so was John the forerunner of His first. And He calls John Elias, to shew that His first coming was agreeable to the Old Testament, and to prophecy.