He who sins is of the devil, for the devil has been sinning from the beginning. To this end the Son of God was revealed, that he might destroy the works of the devil.

 (iii) Further, not to love is to become a murderer. There can be no doubt that John is thinking of the words of Jesus in the Sermon on the Mount ( Matthew 5:21-22). Jesus said that the old law forbade murder but the new law declared that anger and bitterness and contempt were just as serious sins. Whenever there is hatred in the heart a man becomes a potential murderer. To allow hatred to settle in the heart is to break a definite commandment of Jesus. Therefore, the man who loves is a follower of Christ and the man who hates is no follower of his. 