Though Matthew means that the one who sins against another is a member of the Church, he also means that that person is a brother or sister. One needs to avoid scandal or embarrassment as far as possible and so the matter must first be sought to be settled between the offended and the offending party with the offended taking the initiative. If this does not work, then two or three must be taken to the offending party to work for the reconciliation. If this too does not work, then the local church will have to intervene to set things right. If the offending party will not listen even to the members of the Church who might be the leaders or some members of the congregation, then the person concerned must be expelled. Though this may sound harsh and does not seem to fit in with Jesus’ command to forgive innumerable times (18,22), the point seems to be that it is possible that at times the best way to make a person see sense is to resort to harsh measures. Also, the good of the entire community is in view.
Jesus himself will ratify the decision of the community and assures them of his presence when they are gathered together in his name. He also gives them an assurance of their prayers being answered when there is a unity of minds and hearts in the community.
There are some people who are incorrigible. Even with these, however, every attempt must be made to win them over and regard them as part of the community. After everything possible has been done and they still refuse, then they can be left to their own designs.