John Chrysostom — as excerpted in the Catena Aurea on Matthew 18:15-17

“It is to be noted, that onewhile the Lord brings the offender to him whom he has offended; as when he says, If thou remember that thy brother has might against thee, go, be reconciled to thy brother: (Mat. 5:23.) otherwhiles He bids him that has suffered the wrong to forgive his neighbour; as where he says, Forgive us our debts, as we also forgive our debtors. (Mat. 6:12.) Here He has devised yet another method, for He brings him who has been grieved to him that grieved him, and therefore says, If thy brother sin against thee; for because he that did the wrong would not readily come to make amends, because of his shame, He draws to him him that has suffered the wrong; and not only draws him there, but with the very purpose of correcting what was done amiss; whence He says, Go and tell hint his fault.”