The following is an excerpt from The MacArthur New Testament Commentary on 1 Corinthians 5.

I wrote you in my letter not to associate with immoral people; I did not at all mean with the immoral people of this world, or with the covetous and swindlers, or with idolaters; for then you would have to go out of the world. But actually, I wrote to you not to associate with any so–called brother if he should be an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler—not even to eat with such a one. 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. (5:9–13)

The discipline God commands His church to take against the unrepentant is to be of a certain kind and should be exercised within certain bounds. These verses indicate some types of offenses that require discipline and give further explanation as to how the discipline is to be carried out.

In a previous letter (see Introduction) Paul had commanded the Corinthian Christians not to associate with immoral people. Associate with translates sunanamignumi, which literally means “to mix up with.” In this compound form it is more intense and means “to keep intimate, close company with.”

Faithful believers are not to keep close company with any fellow believers who persistently practice serious sins such as those mentioned here. 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.

The Corinthians had misinterpreted Paul’s previous advice about associating with immoral people. I did not at all mean with the immoral people of this world, or with the covetous and swindlers, or with idolaters; for then you would have to go out of the world, he explained. Apparently the church had stopped having contact with unbelievers instead of with unrepentant believers. The apostle pointed out that to do so is impossible without leaving the planet. Besides, sin outside the church is not nearly as dangerous to the church as sin within its own membership. Perhaps their wrong response also reflected their wanting to tolerate sin in the church. And their treatment of the unsaved in the world may have indicated their spiritual arrogance.

It is the world to whom we are to witness, to whom we are called to bring the gospel. We are not to conform to the world (Rom. 12:2), but we must be in the world and have contact with unsaved people or we could never evangelize them. In His high priestly prayer, the Lord prayed, “I do not ask Thee to take them out of the world, but to keep them from the evil one. … As Thou didst send Me into the world, I also have sent them into the world” (John 17:15, 18). We are to “be blameless and innocent, children of God above reproach in the midst of a crooked and perverse generation, among whom [we] appear as lights in the world” (Phil. 2:15). God intends us to be in the world so we can be its salt and light (Matt. 5:13–16) and His witnesses to it (Acts 1:8).

It is the so–called [onomazo, “to bear the name of”] brother who is a threat to the spiritual welfare of a church and with whom we are not to associate. We cannot know who is and is not a true believer, but discipline is to be administered to any who professes to be a Christian. Since we cannot tell the difference, tares must be treated like wheat. Anyone who carries the name of Christ is subject to discipline.

Paul makes it clear that excommunication is not limited only to cases of extreme sin such as that of the incestuous brother who was living with his stepmother. It should be applied to any professing believer who is an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler.

Although true believers are recipients of a new nature—the divine nature, the life of God in their inner person, a new holy self—the flesh is still present and offers the potential for all kinds of sinning. The believer who refuses to appropriate the resources of his new life and yields to the flesh will fall into habitual patterns of evil such as those mentioned here. The Greek terms used here to identify the sins are substantives, indicating patterns of behavior.

Can believers develop such patterns of sin? The answer is yes. In salvation the penalty of sin is paid and the dominion of sin is broken, so that subjection to it is not necessary, but voluntary. Believers who choose sin will develop sinful patterns unless they repent. In 6:9–11 Paul says such unbelievers do not enter the kingdom (salvation), and he assures the Corinthians that they are not like those people anymore. Yet in 6:8 he says that they are acting like them. The point is that in unbelievers there is an unbroken pattern of sinning that cannot be restrained. In believers that unbroken pattern is broken, the frequency and totality of sin is changed. Righteousness and goodness find a place and the life manifests virtue. Because of our humanness, however, sin will sometimes break the pattern of righteousness. If persisted in, it establishes a sinful pattern, interrupting the manifestations of holiness coming from the new nature. That is why there are so many commands and calls to obedience and to church discipline. The believer will never become totally sinful, but may be sinful enough at certain points in his life to be characterized as an unbeliever.

Paul’s thought, as we combine this text with 6:9–11, is that believers can act like unbelievers, those who are shut out of the kingdom. We cannot always tell wheat from tares, or know whether a so–called brother is genuine. Such acts of sin make a believer indistinguishable from a nonbeliever to the world, to the church, and even to himself. All assurance is forfeited (cf. 2 Pet. 1:5–10; 1 John 2:5). It is essential to realize that in a true believer the flow of sin will not be uninterrupted, as in one who is unredeemed. There will be some fruit of righteousness, for the new nature must be manifest (John 15:1–8).

The Corinthian church had members who practiced all of those sins. An immoral member is the primary subject of 1 Corinthians 5. That some were covetous is implied in 10:24; and some were involved in idolatry (10:21–22). Apparently many of them were revilers, or slanderers, running down members of other parties (3:3–4) and likely to despise Timothy when he came to minister to them (16:11). They had drunkards (11:21) and they had swindlers (6:8). The whole epistle reminds us of the sinning capability of believers. All offenders were to be put out of the congregation unless they repented and changed. The rest of the believers were to withdraw from them in any social setting that implied acceptance, and were not even to eat with such a one.

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).