Knowing God through His Word … Day by Day

 If your enemy is hungry, give him bread to eat,
and if he is thirsty, give him water to drink,
for you will heap burning coals on his head,
and the Lord will reward you. —Proverbs 25:21-22

From the ESV Study Bible:

Although interpreters differ about the meaning of the metaphor of heaping burning coals on the enemy’s head, it is likely an image for leading him to repentance or shame, suggesting that he will feel inward burning pangs of guilt for his wrongdoing. In any case, the message is clearly to repay evil with good (see Rom. 12:17–21). The image of “burning coals” does not imply something that harms the enemy, because it further explains the bread and drink in Prov. 25:21, which do him good, and also because Proverbs forbids taking personal vengeance (see 20:22). Finally, the Lord will reward you (25:22) implies a good result from these “burning coals,” which is most consistent with leading the person to repentance.

I found the following at a helpful blog on Bible idioms:

For this to make sense, we need to know that, in Bible lands, almost everything was carried on the head ­ water jars, baskets of fruit, vegetables, fish and other articles.

In many homes, the only fire they had was kept in a metal container, or brazier, which they used for simple cooking as well as for warmth. It was always kept burning. If it ever went out, a family member took the container to a neighbor’s house to borrow fire. Then she would lift the brazier to her head and start for home. If the neighbor was a generous person, she would heap the container full of coals.

To feed an enemy and give him drink was like heaping the empty brazier with live coals ­ which meant food, warmth, and almost life itself to the person or home needing it. “To heap coals of fire upon their heads” was a saying which symbolized the very finest generosity.