Matthew 18:15-17

15“If your brother or sister sins, go and point out their fault, just between the two of you. If they listen to you, you have won them over. 16But if they will not listen, take one or two others along, so that ‘every matter may be established by the testimony of two or three witnesses.’ 17If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector.