By this it appears that, however the scribes and Pharisees had corrupted the law, not only the commandment of loving our brethren, but even that of loving our enemies, was not only a new, but also an old commandment, an Old Testament commandment, though our Saviour has given it to us with the new enforcement of his own great example in loving us when we were enemies. Observe, 1. How we must express our love to our enemies by the real offices of kindness, even those that are expensive to ourselves and most acceptable to them: "If they be hungry and thirsty, instead of pleasing thyself with their distress and contriving how to cut off supplies from them, relieve them, as Elisha did the Syrians that came to apprehend him," Kg2 6:22. 2. What encouragement we have to do so. (1.) It will be a likely means to win upon them, and bring them over to be reconciled to us; we shall mollify them as the refiner melts the metal in the crucible, not only by putting it over the fire, but by heaping coals of fire upon it. The way to turn an enemy into a friend is, to act towards him in a friendly manner. If it do not gain him, it will aggravate his sin and punishment, and heap the burning coals of God's wrath upon his head, as rejoicing in his calamity may be an occasion of God's turning his wrath from him, Pro 24:17. (2.) However, we shall be no losers by our self-denial: "Whether he relent towards thee or no, the Lord shall reward thee; he shall forgive thee who thus showest thyself to be of a forgiving spirit. He shall provide for thee when thou art in distress (though thou hast been evil and ungrateful), as thou dost for thy enemy; at least it shall be recompensed in the resurrection of the just, when kindnesses done to our enemies shall be remembered as well as those shown to God's friends."

For thou shall heap coals of fire upon his head,.... Not to increase his punishment and damnation, the more aggravated by kindness shown him; but to bring him by such means to a sense of former injuries, and to shame for them, repentance of them, and love of the person injured, and carefulness for the future of doing him any further wrong;

and the Lord shall reward thee: with good things, for all the good done to thine enemy, whether it has the desired effect on him or not; or whether he rewards thee or not; see Rom 12:20.

(Compare Mat 5:44; Rom 12:20). As metals are melted by heaping coals upon them, so is the heart softened by kindness.