Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head.
Therefore - or, 'But' (according to a well-supported reading)
If thine enemy hunger, feed him; if he thirst, give him drink. This is taken from Proverbs 25:21-22, which, without doubt, supplied the basis of those lofty precepts on that subject which form the culminating point of the Sermon on the Mount.
For in so doing thou shalt heap coals of fire on his head. The sense of this clause is much disputed. In Jerome's time, and by the Greek interpreters, it was generally understood in the unfavourable sense of aggravating our enemy's guilt-q.d., 'That will be the most effectual vengeance, as effectual as if you heaped coals of fire on his head.' And so, among modern interpreters, Beza, Estius, Grotius, Tholuck, Alford. But Jerome, Augustine, and other Latin fathers, Erasmus, Luther, Bengel, Reiche, Tholuck, Meyer, DeWette, Olshausen, Fritzsche, Philippi, Lange, Hodge (last edition), take the expression in the good sense, in which now it is almost universally quoted-namely, that by returning good for our enemy's evil we may expect at length to subdue and overpower him-as burning coals consume all that is inflammable-into shame and repentance. And though we formerly judged otherwise, we are now constrained to regard this as the true sense. The next verse would seem to confirm this.