Gregory the Great
Catena Aurea · Johannesevangelium 1
And they which were sent were of the Pharisees. And they asked him, and said unto him, Why baptizest thou then, if thou he not that Christ, nor Elias, neither that prophet? John answered them, saying, I baptize with water: but there standeth one among you, whom ye know not; He it is, who coming after me is preferred before me, whose shoe’s latchet I am not worthy to unloose. These things were done in Bethabara beyond Jordan, where John was baptizing.
(Hom. vii. in Evang. c. 3) John baptizeth not with the Spirit, but with water; not being able to remit sins, he washes the bodies of the baptized with water, but not their souls with pardon. Why then doth he baptize, when he doth not remit sins by baptism? To maintain his character of forerunner. As his birth preceded our Lord’s, so doth his baptism precede our Lord’s baptism. And he who was the forerunner of Christ in His preaching, is forerunner also in His baptism, which was the imitation of that Sacrament. And withal he announces the mystery of our redemption, saying that He, the Redeemer, is standing in the midst of men, and they know it not: There standeth one among you, whom ye know not: for our Lord, when He appeared in the flesh, was visible in body, but in majesty invisible.