“If your fellow believer sins against you, go and tell him in private what he did wrong. If he listens to you, you have helped that person to be your brother or sister again.
But whoever hates a brother or sister is in darkness, lives in darkness, and does not know where to go, because the darkness has made that person blind.
So we can see who God’s children are and who the devil’s children are: Those who do not do what is right are not God’s children, and those who do not love their brothers and sisters are not God’s children.
Do not be like Cain who belonged to the Evil One and killed his brother. And why did he kill him? Because the things Cain did were evil, and the things his brother did were good.