Augustine of Hippo

(Tr. lxxx. 3) And who is there in this world so clean, that he cannot be more and more changed? Here, if we say that we have no sin, we deceive ourselves. (1 John 1:8) He cleanseth then the clean, i. e. the fruitful, that the cleaner they be, the more fruitful they may be. Christ is the vine, in that He saith, My Father is greater than I; but in that He saith, I and My Father are one, He is the husbandman; not like those who carry on an external ministry only; for He giveth increase within. Thus He calls Himself immediately the cleanser of the branches: Now ye are clean through the word, which I have spoken unto you. He performs the part of the husbandman then, as well as of the vine. But why does He not say, ye are clean by reason of the baptism wherewith ye are washed? Because it is the word in the water which cleanseth. Take away the word, and what is the water, but water? Add the word to the element, and you have a sacrament. Whence hath the water such virtue as that by touching the body, it cleanseth the heart, but by the power of the word, not spoken only, but believed? For in the word itself, the passing sound is one thing, the abiding virtue another. This word of faith is of such avail in the Church of God, that by Him who believes, presents, blesses, sprinkles the infant, it cleanseth that infant, though itself is unable to believe.