John Chrysostom
And be it noted, that He said not to the Primate1 of the Church, Bind such a man; but, If ye shall bind him, the bonds shall be indissoluble; leaving the other to his discretion. And see how He has set the incorrigible person under the yoke of a twofold necessity; to wit, the punishment that is here, namely, the casting forth out of the Church, when He said, Let him be to thee as a heathen; and the future punishment, saying, that he shall be bound in heaven; thus by the weight of his penalties lessening his brother’s wrath against him.
Or, because He had said, It shall be done unto them by My Father; therefore, to shew that He is the Giver together with His Father, He adds this, where two or three, &c.
Yet He said not barely, Where they are gathered together, but added, in my name, as much as to say, If any man look upon Me as the chief motive of his love to his neighbour, I will be with him, though he is virtue be shewn towards other men. How is it then that those who thus agree together do not obtain what they ask for? First, because they ask things not expedient, and because they do not bring on their parts that which they ought to contribute; wherefore He says, If two of you, that is, who shew an evangelic conversation. Thirdly, because they pray seeking vengeance against those who have grieved them. And fourthly, because they seek mercy for sinners who have not repented.