Attr. to St. Jerome: Who again is mightier than the grace, by which sins are washed away, which John signifies? He who seven times and seventy times seven remits sins (Matt 18:22). Grace indeed comes first, but remits sins once only by baptism, but mercy reaches to the wretched from Adam up to Christ through seventy-seven generations, and up to one hundred and forty-four thousand.
Theophylact (1055-1107): Some persons also understand it thus; all who came to John, and were baptized, through penitence were loosed from the bands of their sins by believing in Christ. John then in this way loosed the sandal straps of all the others, that is, the bands of sin. But Christ’s sandal straps he was not able to unloose, because he found no sin in Him.
The Venerable Bede (672/3-735): in Marc., i, 4: He was baptized, that by being baptized Himself He might show His approval of John’s baptism, and that, by sanctifying the waters of Jordan through the descent of the dove, He might show the coming of the Holy Spirit in the washing of believers.
Whence there follows, “And straightway coming up out of the water, he saw the heavens opened, and the Holy Spirit like a dove descending, and resting upon him.” But the heavens are opened, not by the opening of the elements, but to the eyes of the spirit, to which Ezekiel in the beginning of his book relates that they were opened; or that His seeing the heavens opened after baptism was done for our sakes, to whom the door of the kingdom of heaven is opened by baptism, the washing of rebirth.
Attr. to St. John Chrysostom: Or else, that from heaven sanctification might be given to men, and earthly things be joined to heavenly. But the Holy Spirit is said to have descended upon Him, not as if He then first came to Him, for He never had left Him; but that He might show forth the Christ, Who was preached by John, and point Him out to all, as it were by the finger of faith.
The Venerable Bede (672/3-735): Well indeed in the shape of a dove did the Holy Spirit come down, for it is an animal of great simplicity, and far removed from the malice of gall, that in a figure He might show us that He looks out for simple hearts, and deigns not to dwell in the minds of the wicked.
Attr. to St. Jerome: Again, the Holy Spirit came down in the shape of a dove, because in the Canticles it is sung of the Church: “My bride, my love, my beloved, my dove.”