Matthew Henry Commentary 1 John 3:11-15

"For this is the message which ye heard from the beginning, that we should love one another: not as Cain was of the evil one, and slew his brother. And wherefore slew he him? Because his works were evil, and his brother`s righteous. Marvel not, brethren, if the world hateth you. We know that we have passed out of death into life, because we love the brethren. He that loveth not abideth in death. Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him." — 1 John 3:11-15 (ASV)

We should love the Lord Jesus, value his love, and therefore love all our brothers and sisters in Christ. This love is the special fruit of our faith and a certain sign of our being born again.

But no one who rightly knows the human heart can wonder at the contempt and enmity of ungodly people against the children of God. We know that we have passed from death to life; we may know it by the evidence of our faith in Christ, of which love for our brothers and sisters is one.

This love is not zeal for a party in the common faith, or affection for those who are of the same name and opinions as ourselves. The life of grace in the heart of a regenerate person is the beginning and first principle of a life of glory, of which those who hate their brother or sister in their hearts must be destitute.