1See how great a love the Father has given to us, that we should be called children of God! For this cause the world doesn’t know us, because it didn’t know him. 2Beloved, now we are children of God. It is not yet revealed what we will be; but we know that when he is revealed, we will be like him, for we will see him just as he is. 3Everyone who has this hope set on him purifies himself, even as he is pure.
4Everyone who sins also commits lawlessness. Sin is lawlessness. 5You know that he was revealed to take away our sins, and no sin is in him. 6Whoever remains in him doesn’t sin. Whoever sins hasn’t seen him and doesn’t know him.
7Little children, let no one lead you astray. He who does righteousness is righteous, even as he is righteous. 8He 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. 9Whoever is born of God doesn’t commit sin, because his seed remains in him, and he can’t sin, because he is born of God. 10In this the children of God are revealed, and the children of the devil. Whoever doesn’t do righteousness is not of God, neither is he who doesn’t love his brother. 11For this is the message which you heard from the beginning, that we should love one another— 12unlike Cain, who was of the evil one and killed his brother. Why did he kill him? Because his deeds were evil, and his brother’s righteous.
13Don’t be surprised, my brothers, if the world hates you. 14We know that we have passed out of death into life, because we love the brothers. He who doesn’t love his brother remains in death. 15Whoever hates his brother is a murderer, and you know that no murderer has eternal life remaining in him.
16By this we know love, because he laid down his life for us. And we ought to lay down our lives for the brothers. 17But whoever has the world’s goods and sees his brother in need, then closes his heart of compassion against him, how does God’s love remain in him?
18My little children, let’s not love in word only, or with the tongue only, but in deed and truth. 19And by this we know that we are of the truth and persuade our hearts before him, 20because if our heart condemns us, God is greater than our heart, and knows all things. 21Beloved, if our hearts don’t condemn us, we have boldness toward God; 22so whatever we ask, we receive from him, because we keep his commandments and do the things that are pleasing in his sight. 23This is his commandment, that we should believe in the name of his Son, Jesus Christ, and love one another, even as he commanded. 24He who keeps his commandments remains in him, and he in him. By this we know that he remains in us, by the Spirit which he gave us.
Cain was the first son of Adam and Eve, as well as the brother of Abel. The two brothers offered sacrifices to God, but Abel's animal sacrifice was deemed acceptable, whereas Cain's offering of produce was not. This gave rise to Cain murdering his brother, Abel. We have acquired the statement that Cain made to God after He had challenged Cain regarding this conflict between the brothers, in which Cain said, "Am I my brother's keeper." Due to his sin of murdering Abel, Cain was marked by God and became a vagabond in the earth. When Cain responded to God's punishment of banishment, he responded that this was too great a punishment and that he would be killed by others. In response, God marked him and said that anyone who killed Cain would receive sevenfold the punishment should they do so. The Bible indicates that he traveled in his exile to the land of Nod, which is east of the Garden of Eden.
Genesis 4.1-17, 24, 25; Hebrews 11.4; 1 John 3.12; Jude 11