Therefore, if thine enemy hunger ... - This verse is taken almost literally from Proverbs 25:21-22. Hunger and thirst here are put for want in general. If thine enemy is needy in any way, do him good, and supply his needs. This is, in spirit, the same as the command of the Lord Jesus Matthew 5:44, “Do good to them that hate you,” etc.
In so doing - It does not mean that we are to do this “for the sake” of heaping coals of fire on him, but that this will be the result.
Thou shalt heap ... - Coals of fire are doubtless emblematical of “pain.” But the idea here is not that in so doing we shall call down divine vengeance on the man; but the apostle is speaking of the natural effect or result of showing him kindness. Burning coals heaped on a man’s head would be expressive of intense agony. So the apostle says that the “effect” of doing good to an enemy would be to produce pain. But the pain will result from shame, remorse of conscience, a conviction of the evil of his conduct, and an apprehension of divine displeasure that may lead to repentance. To do this, is not only perfectly right, but it is desirable. If a man can be brought to reflection and true repentance, it should be done. In regard to this passage we may remark,
(1) That the way to promote “peace” is to do good even to enemies.
(2) The way to bring a man to repentance is to do him good. On this principle God is acting continually. He does good to all, even to the rebellious; and he designs that his goodness should lead people to repentance; Romans 2:4. People will resist wrath, anger, and power; but “goodness” they cannot resist; it finds its way to the heart; and the conscience does its work, and the sinner is overwhelmed at the remembrance of his crimes.
(3) If people would act on the principles of the gospel, the world would soon be at peace. No man would suffer himself many times to be overwhelmed in this way with coals of fire. It is not human nature, bad as it is; and if Christians would meet all unkindness with kindness, all malice with benevolence, and all wrong with right, peace would soon pervade the community, and even opposition to the gospel might soon die away.