John Chrysostom
Catena Aurea · Matthäusevangelium 18
Moreover if thy brother shall trespass against thee, go and tell him his fault between thee and him alone: if he shall hear thee, thou hast gained thy brother. But if he will not hear thee, then take with thee one or two more, that in the mouth of two or three witnesses every word may be established. And if he shall neglect to hear them, tell it unto the Church: but if he neglect to hear the Church, let him be unto thee as an heathen man and a Publican.
Yet the Lord enjoins nothing of this sort to be observed towards those who are without the Church, such as He does in reproving a brother. Of those that are without He says. If any smite thee on the one cheek, offer to him the other also. (Mat. 5:39.) as Paul speaks, What have I to do to judge them that are without? (1 Cor. 5:12.) But brethren he bids us reprove, and turn away from.