John 8:
John elaborated in 1 John 3:
Cain killed his brother:
What did the devil do from the beginning as a murderer?44 You are of your father the devil, and your will is to do your father’s desires. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies.
John elaborated in 1 John 3:
The devil deceived our first parents, and they became subject to death.8 Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the works of the devil.
Cain killed his brother:
12 We should not be like Cain, who was of the evil one and murdered his brother. And why did he murder him? Because his own deeds were evil and his brother’s righteous.