8
The person who keeps on sinning is from the Adversary, because from the very beginning the Adversary has kept on sinning. It was for this very reason that the Son of God appeared, to destroy these doings of the Adversary.
9
No one who has God as his Father keeps on sinning, because the seed planted by God remains in him. That is, he cannot continue sinning, because he has God as his Father.
10
Here is how one can distinguish clearly between God's children and those of the Adversary: everyone who does not continue doing what is right is not from God. Likewise, anyone who fails to keep loving his brother is not from God.