Romans 12:20

20.If therefore, etc. He now shows how we may really fulfill the precepts of not revenging and of not repaying evil, even when we not only abstain from doing injury but when we also do good to those who have done wrong to us; for it is a kind of an indirect retaliation when we turn aside our kindness from those by whom we have been injured. Understand as included under the words meat and drink, all acts of kindness. Whatsoever then may be thine ability, in whatever business thy enemy may want either thy wealth, or thy counsel, or thy efforts, thou oughtest to help him. But he calls him our enemy, not whom we regard with hatred, but him who entertains enmity towards us. And if they are to be helped according to the flesh, much less is their salvation to be opposed by imprecating vengeance on them.

Thou shalt heap coals of fire, etc. As we are not willing to lose our toil and labor, he shows what fruit will follow, when we treat our enemies with acts of kindness. But some by coals understand the destruction which returns on the head of our enemy, when we show kindness to one unworthy, and deal with him otherwise than he deserves; for in this manner his guilt is doubled. Others prefer to take this view, that when he sees himself so kindly treated, his mind is allured to love us in return. I take a simpler view, that his mind shall be turned to one side or another; for doubtless our enemy shall either be softened by our benefits, or if he be so savage that nothing can tame him, he shall yet be burnt and tormented by the testimony of his own conscience, on finding himself overwhelmed with our kindness. (398)

It is not true what [Whitby ] and others have held, that “coals of fire” always mean judgments or punishments. The word indeed in certain connections, as in Psalms 18:13, has this meaning, but in Proverbs 25:22, it cannot be taken in this sense, as the preceding verse most clearly proves. There is no canon of interpretation more erroneous than to make words or phrases to bear the same meaning in every place. — Ed.