1. The brother/sister is a person in the faith, a fellow Christian. Put the fault plainly before him/her; show him/her how he had wronged you, and how he has offended God. Correction must be done in private, gently, mercifully. Such treatment may win the heart. If the person owns his fault, and asks for pardon, you have won him for God. A quarrel is loss for both parties and reconciliation is a gain for both parties.
2. If the offender is obdurate and stubborn, do not yet resort to public measures, but make a fresh effort accompanied by a friend or two, who will confirm your expostulation, which might otherwise be consider partial and self-interested.
3. The third step is to inform the Church. Our Lord is contemplating a visible society possessed of certain powers of discipline and correction. Only when the person fails to listen to the Church we will go the extreme action of excommunication. But even in this extreme case charity will not regard the sinner as hopelessly lost; it will seek his salvation by prayer.
4. The Lord solemnly confers the grant made to Peter on the whole apostolate. The binding and losing in a restricted sense and in logical connection with what precedes refer to the confirmation and authorization of the sentence of the Ecclesia.
5. The Lord gives special heed to the joint intercession of all Christians. Two of the followers, even the smallest member could form an association. One’s infirmity is upheld by another’s strength; one’s short-sightedness compensated by another’s wider view; the thing asked must be reasonable, good in itself; the prayer must be earnest, faithful and persevering. The desire will be granted in some form, though not in the way or at the time expected.
All of us have the obligation to correct our own brothers and sisters if they go wrong. But this should be done with great charity. Correction should not be a condemnation but an exhortation which will enable the individual to safeguard from grave harm. At times people may not accept the corrections and moreover they may even react against the one who gives correction. The best way is to pray for that particular individual without nagging them too much. The Lord will take the responsibility for such individuals.
The Pulpit Commentary