“If someone says, “I love God,” and hates his brother, he is a liar; for he who does not love his brother whom he has seen, how can he love God whom he has not seen? 1 Jn 4:20
When we are saved, the Love of God is shed abroad in our hearts (Rom 5:5). This love enables us to love people just as God has loved us. This love also enables us to forgive when others have wronged us. If God has given us the ability and power to love and forgive, how can we hate anyone? How can we have the right to hate anyone when God has forgiven us for all the evil that we did to Him? This is the reason John writes these words in First John. It’s a good way to test yourself to see whether you are in the faith: Do you have hatred in your heart?
If you have hatred in your heart towards anyone for any reason then you don’t really love God, no matter what you say. How can you possibly hate your brother who is right here with you in plain sight and love a God that you have never seen? How can you love a God that you obviously know nothing about, seeing that you hate your brother? Anyone that truly knows God, knows love and, in effect, loves his brother as himself. It is impossible to love God and hate people. It doesn’t work.