“If another believer sins against you, go privately and point out the offense. If the other person listens and confesses it, you have won that person back.
But anyone who hates a fellow believer is still living and walking in darkness. Such a person does not know the way to go, having been blinded by the darkness.
So now we can tell who are children of God and who are children of the devil. Anyone who does not live righteously and does not love other believers does not belong to God.
We must not be like Cain, who belonged to the evil one and killed his brother. And why did he kill him? Because Cain had been doing what was evil, and his brother had been doing what was righteous.