Not to love our brother (verse 14) is no different from hating him, and even murdering him (verse 15), or at least it is the first step along the same path. Let no one therefore comfort himself that he is merely indifferent towards his brother, but feels no positive hatred towards him. The safest way to shut out hatred is to love all God’s children.
Many people feel hatred without committing murder. How then can John say everyone who hates his brother is a murderer? The things which hold us back from doing evil are not things we can take credit for: the fear of punishment, the pain of a guilty conscience, the shame of being discovered, or the fear of revenge. Yet by these things God frequently restrains men from doing the evil that they would like to do.