Tertullian

“ Ask (yourself) whether the law of not committing adultery be still in force, to which has been added that of not indulging concupiscence. Besides, if any precedents (taken from the Old Dispensation) shall favour you in (the secrecy of) your bosom, they shall not be set in opposition to this discipline which we are maintaining. For it is in vain that an additional law has been reared, condemning the origin even of sins—that is, concupiscences and wills—no less than the actual deeds ”

“ We, too, indeed have precedents in the self-same antiquity on the side of our opinion,— (precedents) of judgment not merely not waived, but even summarily executed upon fornication. And of course it is a sufficient one, that so vast a number— (the number) of 24,000—of the People, when they committed fornication with the daughters of Madian, fell in one plague. ”

“ But Even the Old Has Examples of Vengeance Upon Such Offences.
Plainly, if you show by what patronages of heavenly precedents and precepts it is that you open to adultery alone—and therein to fornication also—the gate of repentance, at this very line our hostile encounter will forthwith cross swords. Yet I must necessarily prescribe you a law, not to stretch out your hand after the old things, [1] not to look backwards: [2] for “the old things are passed away,” [3] according to Isaiah ”