Romans 6:1

He is again turning off to exhortation, yet introducing it not directly, lest he should seem to many to be irksome and vexing, but as if it rose out of the doctrines. For if, even so diversifying his address, he was afraid of their being offended at what he said, and therefore said, "I have written the more boldly unto you in some sort," much more would he have seemed to them, had he not done so, to be too harsh. Since then he showed the greatness of the grace by the greatness of the sins it healed, and owing to this it seemed in the eyes of the unthinking to be an encouragement to sin (for if the reason, they would say, why greater grace was shown, was because we had done great sins, let us not give over sinning, that grace may be more displayed still), now that they might not say this or suspect it, see how he turns the objection back again. First he does it by his deprecation. "God forbid." And this he is in the habit of doing at things confessed on all hands to be absurd. And then he lays down an irrefragable argument.