An excerpt from "Got Questions.org" entitled, "What does it mean to bless those who curse you (Luke 6:28)?" states: "It is one thing to bless or pray for someone who is doing good to you, but to bless or pray for those who curse you is very different. To curse (kataromenous) is to cause harm or to persecute (as in Matthew 5:44). Jesus is telling His listeners that the way to respond to one who seeks to harm us is to pray for his good. Obviously, if we are motivated by self-interest, we would never pursue the good of our enemies. But Jesus is challenging His listeners to work from truly selfless love and concern for the other. When we are acting for the benefit of someone else—even when it is undeserved—an incredible side benefit is that we ourselves are blessed. Jesus says that the reward for such behavior is great (Luke 6:35). He adds that, if we are forgiving, we also are forgiven or pardoned (Luke 6:37). If we give, it will be given to us (Luke 6:38). To bless those who curse us requires that we are motivated by a desire for their well-being. When we treat others with that kind of love, God sees, and He rewards." This article may be viewed at: What does it mean to bless those who curse you?/gotquestions.org
Reference: Romans 12:14