Chapter 15 [XIV.]—Not Everything [of Doctrinal Truth] is Written in Scripture in So Many Words.
That, too, which is said to him, “that it is nowhere written in so many words, A man can be without sin,” he easily refutes thus: “That the question here is not in what precise words each doctrinal statement is made.” It is perhaps not without reason that, while in several passages of Scripture we may find it said that men are without excuse, it is nowhere found that any man is described as being without sin, except Him only, of whom it is plainly said, that “He knew no sin.” 1156 Similarly, we read in the passage where the subject is concerning priests: “He was in all points tempted like as we are, only without sin,” 1157 —meaning, of course, in that flesh which bore the likeness of sinful flesh, although it was not sinful flesh; a likeness, indeed, which it would not have borne if it had not been in every other respect the same as sinful flesh. How, however, we are to understand this: “Whosoever is born of God doth not commit sin; neither can he sin, for his seed remaineth in him;” 1158 while the Apostle John himself, as if he had not been born of God, or else were addressing men who had not been born of God, lays down this position: “If we say that we have no sin, we deceive ourselves, and the truth is not in us,” 1159 —I have already explained, with such care as I was able, in those books which I wrote to Marcellinus on this very subject. 1160 It seems, p. 126 moreover, to me to be an interpretation worthy of acceptance to regard the clause of the above quoted passage: “Neither can he sin,” as if it meant: He ought not to commit sin. For who could be so foolish as to say that sin ought to be committed, when, in fact, sin is sin, for no other reason than that it ought not to be committed?
See the De Peccat. Meritis et Remissione, ii. 8–10.