Let us then not be ashamed to confess our sins unto the Lord. Shame indeed there is when each makes known his sins, but that shame, as it were, ploughs his land, removes the ever-recurring brambles, prunes the thorns, and gives life to the fruits which he believed were dead. Follow him who, by diligently ploughing his field, sought for eternal fruit: "Being reviled we bless, being persecuted we endure, being defamed we entreat, we are made as the offscouring of the world." If you plough after this fashion you will sow spiritual seed. Plough that you may get rid of sin and gain fruit. He ploughed so as to destroy in himself the last tendency to persecution. What more could Christ give to lead us on to the pursuit of perfection, than to convert and then give us for a teacher one who was a persecutor?
Ambrose, Concerning Repentance, Book II. Ambrose is talking, of course, of St. Paul.