The Enchiridion by St. Augustine
Chapter 49.--Christ Was Not Regenerated in the Baptism of John, But Submitted to It to Give Us an Example of Humility, Just as He Submitted to Death, Not as the Punishment of Sin, But to Take Away the Sin of the World.
Now, those who were baptized in the baptism of John, by whom Christ was Himself baptized, were not regenerated; but they were prepared through the ministry of His forerunner, who cried, |Prepare ye the way of the Lord,| for Him in whom only they could be regenerated. For His baptism is not with water only, as was that of John, but with the Holy Ghost also; so that whoever believes in Christ is regenerated by that Spirit, of whom Christ being generated, He did not need regeneration. Whence that announcement of the Father which was heard after His baptism, |This day have I begotten Thee,| referred not to that one day of time on which He was baptized, but to the one day of an unchangeable eternity, so as to show that this man was one in person with the Only-begotten. For when a day neither begins with the close of yesterday, nor ends with the beginning of to-morrow, it is an eternal to-day. Therefore He asked to be baptized in water by John, not that any iniquity of His might be washed away, but that He might manifest the depth of His humility. For baptism found in Him nothing to wash away, as death found in Him nothing to punish; so that it was in the strictest justice, and not by the mere violence of power, that the devil was crushed and conquered: for, as he had most unjustly put Christ to death, though there was no sin in Him to deserve death, it was most just that through Christ he should lose his hold of those who by sin were justly subject to the bondage in which he held them. Both of these, then, that is, both baptism and death, were submitted to by Him, not through a pitiable necessity, but of His own free pity for us, and as part of an arrangement by which, as one man brought sin into the world, that is, upon the whole human race, so one man was to take away the sin of the world.