Luther

The discipline of the flesh follows, to mortify its coarse and evil lust and win peace and rest. Such lusts must be overcome with fasting and watching and work. Thus we learn why and how much we should fast, watch, and work…. Therefore I leave it to every man to choose for himself the days, the food, and the amount of fasting, but he must not leave it at that, but keep watch over his flesh; inasmuch as he finds it lascivious and wanton, he should discipline it with fasting, watching, working, and more.—Sermon on Good Works, 1520