Problem: Paul’s reference to “burning coals” on someone’s head is very bizarre. Critics interpret this to mean that Christians should literally burn their enemies with fire.
Solution: This reference to burning coals is obviously a metaphorical way to describe how to respond to our enemies. In fact, this verse is sandwiched by the language of non-violence! Verse 19 states, “Never take your own revenge,” and verse 21 states, “Do not be overcome by evil, but overcome evil with good.” Therefore, a literalistic interpretation of verse 20 would be absurd. Instead, this imagery comes from the OT. In fact, this is a citation of Proverbs 25:21-22. However, in addition to mentioning “burning coals,” the author of Proverbs adds on “and the Lord will reward you.” Therefore, this is not an act of cruelty; it is an act of kindness. This concept of burning coals is a symbol of repentance and forgiveness for sin in the OT. For instance, in Isaiah 6:7 we read: “He touched my mouth with it [the burning coals from the altar] and said, ‘Behold, this has touched your lips; and your iniquity is taken away and your sin is forgiven.’” God’s purpose in burning the coal on Isaiah’s lips was to forgive him. In the same way, by burning coals on an aggressors head, we are extending forgiveness.
“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. (Rom 12:20)