"If your enemy is hungry, give him food to eat; if he is thirsty, give him water to drink." (Proverbs 25:21)
It is the glory of God to conceal a matter; to search out a matter is the glory of kings. Like the heavens for height and the earth for depth, so the hearts of kings are unsearchable. Remove the dross from the silver, and a silversmith can produce a vessel. Like a city whose walls are broken through is a person who lacks self-control. Like a snow-cooled drink at harvest time is a trustworthy messenger to the one who sends him. If your enemy is hungry, give him food to eat; if he is thirsty, give him water to drink. In doing this, you will heap burning coals on his head, and the LORD will reward you. Like a fluttering sparrow or a darting swallow, an undeserved curse does not come to rest.
The Catechism identifies this proverb as one of the Old Testament foundations of the New Testament command to love enemies: the active good done to an enemy is the most powerful form of moral persuasion and the way God rewards the generous (CCC 1933). Paul quotes this passage directly in Romans 12:20.
Brothers and sisters, give your enemy food and water. Not because they deserve it, not because it is easy, not because it will make you feel good in the moment - but because the LORD will reward you, and because the burning coals of kindness have a better chance of changing a heart than the burning coals of retaliation.
Lord God, give us the courage to feed our enemies. Through Christ our Lord. Amen.