He who says he is in the light and hates his brother, is in the darkness even until now.
Jesus said, "This is the commandment that I give unto you, that ye love one another" ( John 13:34-35 ). I can say, "Oh yes, I have His commandments, He told me to love one another," and yet, you hate everybody. You see, having the commandment isn't enough. How can I know that I know Him? If I keep His commandment!