Matthew Henry Commentary Proverbs 25:21-22

"If thine enemy be hungry, give him bread to eat; And if he be thirsty, give him water to drink: For thou wilt heap coals of fire upon his head, And Jehovah will reward thee." — Proverbs 25:21-22 (ASV)

The precept to love even our enemies is an Old Testament commandment. Our Saviour has shown his own great example in loving us when we were enemies.