Romans 12:19-21
19 Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written,“Vengeance is mine, I will repay, says the Lord.” 20 To the contrary, “if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by so doing you will heap burning coals on his head.” 21 Do not be overcome by evil, but overcome evil with good.
My dad used to say, "You catch more flies with honey than with vinagar." In a sense, Paul is telling the Romans a similar thing althugh the motives may not be the same. As Christians, we must cultivate our ability to love and the first step to doing so is to eliminate hate. Now hate can exist in some people at all times but for most of us, it is more of a spur of the moment emotion that gets triggered by things that annoy us. For instance, my wife sometimes can be so unreasonable and downright mean when she gets in a bad mood. When she gets that way, I feel like shouting back at her but instead I give her a hug and tell her I love her. My anger immediately dissipates and hers eventually does as well.
Paul says by loving our enemies, we heap burning coals on their heads. I prefer to think of it as pouring cool water on the burning coals in theor hearts. Whenever the anger and hate well up, I pray and use kindness and soft words to overcome my emotions and it usually translates into everyone involved calming down. Evil is overcome with good.