What does 1 John 3:15 mean?

John's words in this verse have led to much controversy. Some have interpreted this to mean that anyone who has committed murder cannot become a Christian. Or, that they never were a Christian. Or that feeling hate towards a fellow Christian is an absolute sign of being lost without Christ.

The context provides a different solution. In verse 12, John has just warned believers, "We should not be like Cain." Cain murdered his brother because of his own evil deeds. Verse 15 builds on this idea. The person who hates his brother is, like Cain, a murderer. Such a person is not "abiding" in eternal life (1 John 2:9, 11). Under no circumstances can a Christian excuse hatred for another believer: such attitudes are entirely from the Devil. Those who persist in such attitudes, more likely than not, have no relationship with Christ at all.

John will build on this further in 1 John 4:20, adding, "If anyone says, ‘I love God,' and hates his brother, he is a liar; for he who does not love his brother whom he has seen cannot love God whom he has not seen." Love is not merely a feeling, it is a choice to act. Hatred is always an act of disobedience to God.