In the first part of my answer, I dealt with one of three ends that formal church discipline is designed to achieve. Here are the other two.

Church discipline is designed to keep the church pure. This end we draw out of a systematic study of this subject from the New Testament. Tolerate no practice of sin in the assembly. Once allowed to fester, sin will negatively influence the rest of the body and bring disastrous consequences. This is Paul’s point in 1 Corinthians 5, where he castigates the Church of Corinth for boasting about an unrepentant member, rather than mourning over him and removing him (v. 2). He says in verse 6, “Your boasting is not good. Do you not know that a little leaven leavens the whole lump of dough?” There’s the principle at work: tolerate sinful behavior in the body and it will eventually have a corrupting influence (cf. 1 Corinthians 15:55). Paul’s solution is found in verse 7, “Clean out the old leaven, that you may be a new lump . . .” It is important to clarify at this point, that removal in formal church discipline means taking the unrepentant believer out of membership—which is why every church should have membership; Without it, you can’t practice disciple. It does not mean to shun the person under disciple and exclude him from hearing the regular preaching and teaching that comes from the pulpit. What better place for an unrepentant person to be in than in hearing distance of the Word?

Finally, church discipline is designed to protect the name of Christ from being tainted. Jesus said that we are to be his witness in the world (Acts 1:8), and we must be careful to represent him accurately. This is why the apostle Paul was always careful to point out that our Christian reputations in the world are very important (Titus 2 and 3). The behavior of the church gathered is no exception. We see this clearly in his rebuke to the Corinthians over the issue of abusing spiritual gifts (see 1 Corinthians 14:23-25).

Some are under the mistaken impression that once a member is removed from the church membership church discipline stops. The argument seeks supports from the idea that since we are now treating the one removed from membership as we would an unbeliever, and unbelievers cannot be disciplined, he is no longer under discipline. There are several reasons why this view is false. First, this view militates against goal of church discipline, which is repentance and restoration. Discipline does not end until there is restoration. Remember, it is designed to produce a good end. Second, God’s discipline never stops. While still a member, the unrepentant believer receives God’s discipline through the channel of the local church. Once membership has been taken away, God now uses other channels to carry out His discipline, specifically Satan. Paul puts it this way in 1 Corinthians 5:5, “I have decided to deliver such a one to Satan for the destruction of his flesh, that his spirit may be saved in the day of the Lord.” God will buffet the one he loves even to the degree that He allows Satan to oppress him, in order to bring about repentance. Third, he and a natural outgrowth of the first two, is that this person is not free to worship at another church until he has sought forgiveness from the church that disciplined him. Before any church receives anyone, it ought always to make sure that he has not received church discipline from another church. Someone who has been is under discipline must be urged lovingly to return to his church to be reconciled with it. Third, while this person is treated as an unbeliever, he is not treated as one in ever respect. There is a difference between a person who claims no association with Christ and attends a worship service out of curiosity, on the one hand, and a person who claims to be a Christian and lives an unrepentant life, on the other. We are free to enjoy the company of the unbeliever and even participate in sports or social events with him. The disciplined believer, however, should receive our undivided and loving attention only for the purpose of addressing his sinful lifestyle.