Augustine of Hippo, Against Two Letters of the Pelagians I.20: In Me, that Is, in My Flesh

And he declares both more plainly in what follows: “For I delight in the law of God after the inward man; but I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.” But in that he said, “bringing me into captivity,” he can feel emotion without consenting to it. Whence, because of those three things, two, to wit, of which we have already argued, in that he says, “But I am carnal,” and “Sold under sin,” and this third, “Bringing me into captivity in the law of sin, which is in my members,” the apostle seems to be describing a man who is still living under the law, and is not yet under grace. But as I have expounded the former two sayings in respect of the still corruptible flesh, so also this latter may be understood as if he had said, “bringing me into captivity,” in the flesh, not in the mind; in emotion, not in consent; and therefore “bringing me into captivity,” because even in the flesh there is not an alien nature, but our own. As, therefore, he himself expounded what he had said, “For I know that in me, that is, in my flesh, dwelleth no good thing,” so also now out of the exposition of that we ought to learn the meaning of this passage, as if he had said, “Bringing me into captivity,” that is, “my flesh,” “to the law of sin, which is in my members.”