Glossa Ordinaria
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.
(ap. Anselm.) Or, tell it to the whole Church, that his infamy may be the greater. After all these things follows excommunication, which ought to be inflicted by the mouth of the Church, that is, by the Priest, and when he excommunicates, the whole Church works with him; as it follows, And if he will not hear the Church, let him by unto thee as an heathen, and a publican.