"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." Paul writing to the Romans (12:20). Can't cite that verse without the next one (vs. 21): "Be not overcome with evil, but overcome evil with good."
It's one thing to "turn to him the other [cheek]" as Jesus says in Matthew's Gospel (5:39). Quite another to literally give something to someone to fulfill a need, if they've mistreated you. It takes time and effort to acquire the food in the first place. When they see that you're willing to give what you worked for, with honest heart and pure motive, something happens to them. Don't look for an outward response though. This all seems like pretty elementary stuff. Simply explained and easier to live out the more you do it. But here's another way of looking at it.
Have you ever thought about that Romans passage with reference to yourself? Not sure if it's meant to be conveyed along those lines, but I will say that the hardest person to forgive oftentimes, is us. One of the firmest convictions I have regarding God, is that He always looks upon us with eyes of love. There are all sorts of variables here, such as the whole love/judgment paradox and the fact that some people actively hate Him and continue to do wrong, in spite of professing an aligned moral compass. Work through those. I'm referring, right now, to God's response to our mistakes. The ones we do that hurt others, however inadvertently. The deeper we get in relation to others, the more chance there is for that fine line to be crossed, and to rub someone the wrong way. I've done it before and I always hate it. I tell myself that I could've waited. Could've prayed more about the fine points of the relationship and not said the thing I did. Here's what silences those nagging thoughts: Jesus forgives me upon asking. It's as simple as that. There's no way that I love myself more than He. But that's exactly the reason why I hold out and refuse to let it go. I tell myself that I care for and love myself more than Him. And that's not correct. Forgive yourself as readily as you're called to forgive others. Overcome evil with good.
As an aside, when Isaiah stood in the presence of God and saw the angel take the live coal from the fire and put it in his mouth, the angel then told him "lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin is purged." (Isaiah 6:6-7) When Paul refers to feeding our enemies, ourselves included, it's understood that we've taken pains to forgive them prior to doing so. Our motive of heart remains pure when we've forgiven the offense, in them and in ourselves.
"Then David arose from the earth, and washed, and anointed himself, and changed his apparel, and came into the house of the Lord, and worshipped: then he came to his own house; and when he required, they set bread before him, and he did eat. Then said his servants unto him, What thing is this that thou hast done? thoud didst fast and weep for the child, while it was alive; but when the child was dead, thou didst rise and eat bread." (2 Samuel 12:20-21)
David might seem calloused and uncaring. What he's showing here is radical self-forgiveness after having repented.