Augustine of Hippo
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.
(Serm. 82, 7.) When any one therefore offends against us, let us be very careful, not for ourselves, for it is glorious to forget an injury; forget therefore your own wrong, but not the wound your brother has sustained; and tell him of his fault between him and you alone, seeking his amendment and sparing his shame. For it may be that out of shame he will seek to defend his fault, and thus you will only harden, while you sought to do him good.