Proverbs 25:22

for you will heap coals of fire on his head, ¹  and the Lord will reward you. ² 

2Sa 16:12; Mt 10:13; 1Co 15:18

¹ sn The imagery of the “burning coals” represents pangs of conscience, more readily effected by kindness than by violence. These coals produce the sharp pain of contrition through regret (e.g., 18:19; 20:22; 24:17; Gen 42-45; 1 Sam 24:18-20; Rom 12:20). The coals then would be an implied comparison with a searing conscience.

² sn The second consequence of treating enemies with kindness is that the Lord will reward the act. The fact that this is promised shows that the instruction here belongs to the religious traditions of Israel.