Augustine of Hippo, Against Two Letters of the Pelagians I.16: How Sin Died, and How It Revived

And what he says in that passage of the Epistle to the Romans, “Sin, that it might appear sin, wrought death to me by that which is good,” agrees with the former passages where he said, “But I had not known sin but by the law, for I had not known lust unless the law had said, Thou shalt not covet.” And previously, “By the law is the knowledge of sin,” for he said this also here, “that it might appear sin;” that we might not understand what he had said, “For without law sin was dead,” except in the sense as if it were not, “it lies hidden, it does not appear, it is completely ignored, as if it were buried in I know not what darkness of ignorance.” And in that he says, “And I was alive once without the law,” what does he say except, I seemed to myself to live? And with respect to what he added, “But when the commandment came, sin revived,” what else is it but sin shone forth, became apparent? Nor yet does he say lived, but revived. For it had lived formerly in Paradise, where it sufficiently appeared, admitted in opposition to the command given; but when it is inherited by children coming into the world, it lies concealed, as if it were dead, until its evil, resisting righteousness, is felt by its prohibition, when one thing is commanded and approved, another thing delights and rules: then, in some measure sin revives in the knowledge of the man that is born, although it had lived already for some time in the knowledge of the man as at first made.