Mat. 18:15-20
If your brother does something wrong, go and have it out with him alone, between your two selves. If he listens to you, you have won back your brother. If he does not listen, take one or two others along with you: whatever the misdemeanour, the evidence of two or three witnesses is required to sustain the charge. But if he refuses to listen to these, report it to the community; and if he refuses to listen to the community, treat him like a gentile or a tax collector.