Augustine of Hippo
Catena Aurea · Matthäusevangelium 3
Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him. But John forbad Him, saying, I have need to be baptized of Thee, and comest Thou to me? And Jesus answering said unto him, Suffer it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered Him.
(non occ. cf. Ambrosiast. Serm. xii. 4.) The Saviour willed to be baptized not that He might Himself be cleansed, but to cleanse the water for ush. From the time that Himself was dipped in the water, from that time has He washed away all our sins in water. And let none wonder that water, itself corporeal substance, is said to be effectual to the purification of the soul; it is so effectual, reaching to and searching out the hidden recesses of the conscience. Subtle and penetrating in its own nature, made yet more so by Christ’s blessing, it touches the hidden springs of life, the secret places of the soul, by virtue of its all-pervading dew. The course of blessing is even yet more penetrating than the flow of waters. Thus the blessing which like a spiritual river flows on from the Saviour’s baptism, hath filled the basins of all pools, and the courses of all fountains.