For what have I to do with judging outsiders? Do you not judge those who are within the church? But those who are outside, God judges. Remove the wicked man from among yourselves. (1 Corinthians 5:12-13)
Faithful believers are not to keep close company with any fellow believers who persistently practice serious sins such as those mentioned in 1 Corinthians 5. If the offenders will not listen to the counsel and warning of two or three other believers and not even of the whole church, they are to be put out of the fellowship. They should not be allowed to participate in any activities of the church—worship services, Sunday school, Bible studies, or even social events. Obviously, and most importantly, they should not be allowed to have any leadership role. They should be totally cut off both from individual and corporate fellowship with other Christians, including that of eating together (v. 11; cf. 2 Thess. 3:6--15).
No exceptions are made. Even if the unrepentant person is a close friend or family member, he is to be put out. If he is a true believer he will not lose his salvation because of the sin (v. 5), but he is to lose contact with fellow believers, in order not to corrupt them with his wickedness and to suffer the consequences of his sin. The pain of such isolation may drive the person to repentance.
A church that does not discipline a sinning member is like a person who has good reason to believe he has cancer but who refuses to go to a doctor—because he either does not want to face the problem or does not want to face the treatment. If he waits too long his whole body will be permeated with the disease and it will be too late for treatment to do any good. No church is healthy enough to resist contamination from persistent sin in its midst, any more than the healthiest and most nutritious bushel of apples can withstand contamination from even a single bad one. The only solution in both cases is separation.
We have no responsibility for judging outsiders. We are to witness to outsiders, but not judge them. We cannot chasten them, and no remedial steps will alter the sin of the ungodly. Those who are outside, God judges. But we do have a responsibility to judge those who are within the church. We must remove the wicked man from among [our]selves.
Discipline is difficult, painful, and often heartrending. It is not that we should not love the offenders, but that we should love Christ, His church, and His Word even more. Our love to the offenders is not to be sentimental tolerance but correcting love (cf. Prov. 27:6)
It is not that everyone in the church must be perfect, for that is impossible. Everyone falls into sin and has imperfections and shortcomings. The church is in some ways a hospital for those who know they are sick. They have trusted in Christ as Savior and they want to follow Him as Lord—to be what God wants them to be. It is not the ones who recognize their sin and hunger for righteousness who are to be put out of fellowship, but those who persistently and unrepentantly continue in a pattern of sin about which they have been counseled and warned. We should continue to love them and pray for them that they repent and return to a pure life. If they do repent we should gladly and joyfully "forgive and comfort" them and welcome them back into fellowship (2 Cor. 2:7)...