3 Why was John sent baptizing? Already, I recollect, I have explained that to you, beloved, according to my ability. For if the baptism of John was necessary for our salvation, it ought even now to be used. For we cannot think that men are not saved now, or that more are not saved now, or that there was one salvation then, another now. If Christ has been changed, the salvation has also been changed; if salvation is in Christ, and Christ Himself is the same, there is the same salvation to us. But why was John sent baptizing? Because it behooved Christ to be baptized. Wherefore did it behoove Christ to be baptized? Wherefore did it behoove Christ to be born? Wherefore did it behoove Christ to be crucified? For if He had come to point out the way of humility, and to make Himself the way of humility; in all things had humility to be fulfilled by Him. He deigned from this to give authority to His own baptism, that His servants might know with what alacrity they ought to run to the baptism of the Lord, when He Himself did not refuse to receive the baptism of a servant. This favor was bestowed upon John that it should be called his baptism.
Source: Tractates on the Gospel of John (New Advent)