Matthew 18:15-18

If one of my followers sins against you, go and point out what was wrong. But do it in private, just between the two of you. If that person listens, you have won back a follower. But if that one refuses to listen, take along one or two others. The Scriptures teach that every complaint must be proved true by two or more witnesses. If the follower refuses to listen to them, report the matter to the church. Anyone who refuses to listen to the church must be treated like an unbeliever or a tax collector. I promise you that God in heaven will allow whatever you allow on earth, but he will not allow anything you don't allow.