And this is the record of John, when the Jews sent priests and Levites from Jerusalem to ask him, Who are you?
All Commentaries on John 1:19 Go To John 1
Augustine of Hippo
AD 430
They would not have sent, unless they had been impressed by his lofty exercise of authority, in daring to baptize.
For they knew that Elias was to preach Christ; the name of Christ not being unknown to any among the Jews; but they did not think that our Lord was the Christ: and yet did not altogether imagine that there was no Christ about to come. In this way, while looking forward to the future, they mistook at the present.
Or because John was more than a prophet: for that the prophets announced Him afar off, but John pointed Him out actually present.
So spoke Esaias: the prophecy was fulfilled in John the Baptist.