John Chrysostom

What then, if he should disobey, and be disposed to abide in hardness? "Take with thyself yet one or two, that in the mouth of two witnesses every word may be established." For the more he is shameless, and bold, the more ought we to be active for his cure, not in anger and indignation. For the physician in like manner, when he sees the malady obstinate, doth not give up nor grow impatient, but then makes the more preparation; which He commands us to do in this case too. …

Homily on the Gospel of Matthew 60 ↗

Augustine of Hippo

If someone has done you injury and you have suffered, what should be done? You have heard the answer already in today's Scripture: "If your brother sins against you, go and tell him his fault, between you and him alone."If you fail to do so, you are worse than he is. He has done someone harm, and by doing harm he has stricken himself with a grievous wound. Will you then completely disregard your brother's wound? Will you simply watch him stumble and fall down? Will you disregard his predicament? …

Sermon 82.7 ↗

Jerome

For in saving another, salvation is gained for ourselves also. Chrys What you should do if he does not yield is added, If he will not hear thee, take with thee one or two. For the more shameless and stubborn he shows himself, the more studious should we be of applying the medicine, and not turn to wrath and hate. As the physician, if he see that the disease does not abate, he does not slack, but redoubles his efforts to heal. …

Catena Aurea by Aquinas ↗

Thomas Aquinas

And if he will not hear you, take with you one or two more. Here he introduces testimony: take one or two, etc. Deut 19:15: in the mouth of two or three witnesses shall every word stand. But here a question arises: why does he not immediately bring in witnesses? It must be said that conscience should be cleansed in such a way that reputation is not harmed: hence if first and by himself he can succeed, well and good; if not, then let him call witnesses. And Jerome says, first one, and then two. And why? …

Commentary on Matthew ↗