5:1–2a The report Paul has heard has two parts: (1) “there is sexual immorality among you,” and (2) “you are arrogant” (cf. v. 6a).

The specific kind of sexual immorality is incest—a man is pursuing sexual relations with his father’s wife. In the phrase “has his father’s wife,” has indicates ongoing sexual relations but does not specify if the two people have married or are cohabiting.49 Because Paul writes “his father’s wife” (rather than “his mother”), he probably refers to this man’s stepmother. She may be roughly the same age as (or even younger than) the incestuous man, since men often married women who were much younger.

The sins Paul corrects throughout this letter were common practices in Corinth. The church in Corinth has grown up in this pagan context that views sex much differently than Jews and Christians did. And since the Corinthians have converted only recently (no more than three years before Paul writes this letter) and do not have generations of Christians in their culture, it is not surprising that they continue to share Corinth’s worldly values regarding sex. Jews, of course, forbade a father and son from sleeping with the same woman (Lev. 18:7–8; 20:11; Deut. 22:30; 27:20). But so did the ancient pagan Romans. Thus Paul describes this sexual immorality as “of a kind that is not tolerated even among [the] pagans.”50

So how is it that the Corinthian church tolerates a sin that even their own culture repudiates? The text does not answer this question, so we can only guess. It could be related to their view of the body and the resurrection (cf. comments on 1 Cor. 6:12–20; 15:1–58). But it is unlikely that the Corinthians boast about tolerating incest, since incest was scandalous in both Jewish and Roman cultures. Most likely, the Corinthians ignore the incest and boast that a man with such a high social status is a member of their church. The incestuous man is likely socially powerful, and the church is simultaneously (1) honored that a person with such a prominent status would be part of their congregation and (2) unwilling to confront him about his incest. He might be a generous benefactor to the church and a patron to clients within the church. Thus the church does what their culture occasionally does for socially prominent people: turn a blind eye to that person’s sin rather than risk losing his favor and becoming his enemy.51

5:2bc Paul first rebukes the Corinthians with a rhetorical question. In contrast to how they are being arrogant, they should mourn over the man’s publicly scandalous and characteristically unrepentant sin, which entails that they should remove the incestuous man from their church.

Throughout this passage Paul exhorts the Corinthian church to excommunicate this man, a church member who claims to be a brother in Christ.52 Consequently, chapter 5 is one of the most significant NT passages for three interrelated theological issues: excommunication, church membership, and congregational church government (I list those three issues from what is more explicit in Scripture to less explicit).53

Excommunication. A local church removes a person from its membership and does not let him celebrate the Lord’s Supper with them. The church does this when the church can no longer affirm that a professing believer is a genuine believer. This is the final step of corrective church discipline.54 Matthew 18:15–17 presents four steps of corrective discipline: (1) a fellow church member confronts a professing believer privately; (2) a small group confronts the professing believer privately; (3) a church member notifies the church about the situation; (4) the church excommunicates the unrepentant professing believer. First Corinthians 5 begins with the final step in Matthew 18 because (1) the church already knows about the incestuous man’s sin; (2) he is unrepentant; and (3) his sin is so scandalous that it undermines his claim to be a brother (i.e., the church cannot publicly affirm that he is a genuine believer).55

Church membership. A local church publicly affirms (as best they can discern) that a person is a genuine believer; that church promises to oversee that person’s discipleship; and that person promises to follow Jesus faithfully as part of that local church (which includes submitting to the church’s elders). Three perspectives show why church membership is important: (1) It helps a church’s elders know for whom they will give account to God. (2) It helps a church’s members mature as Christians and enables them to practice church discipline on fellow members (1 Corinthians 5 presupposes church membership, because a church cannot practice church discipline without it). (3) It helps the world know who professing Christians are. Submitting to a church is not like joining a club; it is more like an embassy in a host nation declaring that a person is a citizen of its home nation. A church declares that a person is a citizen of God’s kingdom.56

Congregational church government. What distinguishes different views on how to govern the church is the determination of who holds final authority: the bishop (episcopal), the presbytery (presbyterian), the elders (elder-rule), or the congregation (congregational). While godly, mature Christians disagree on which model is most biblical, I think the most biblical polity is elder-led and congregation-ruled.57 This model is very different from a modern democracy, in which leaders represent the people and the people make demands on the leaders with the threat that they will vote them out of office; it is more like a combination of a monarchy (Jesus is the King), a senate (elders lead), and a democracy (members vote on certain important matters).58 I believe 1 Corinthians 5 supports congregational church government because Paul appeals not directly to the church leaders but to the whole church to excommunicate the incestuous man. Some might retort that in chapter 5 the church is merely to carry out what the apostle Paul has already decided for them (v. 3). But Paul supports his argument with a principle: “Is it not those inside the church whom you are to judge?” (v. 12b). The church as a whole—not just the leaders—is responsible to practice church discipline. Paul uses the case of the incestuous man to train the church in how to act responsibly on their own in the future.

5:3–5 Why should the Corinthians remove the incestuous man from among them (v. 2c)? Because Paul has already judged him. Paul has done so as if he were physically present in Corinth even though he is not. Consequently, the Corinthians must carry out this judgment when they assemble.

Verses 3–5 are a single sentence in Greek. Based on form it could be translated as follows, starting with the end of verse 3 (with the words in bold being the main clauses):

5:6 Paul again rebukes the Corinthians (cf. v. 2b). Then he gives a reason their boasting is not good: “a little leaven leavens the whole lump.”61

Leaven is not identical to yeast, which was “foreign to ancient baking” (BDAG, s.v. ζύμη). But it worked like yeast does today: adding a little leaven (i.e., a small bit of fermented dough from the previous batch) to a new batch of dough made the whole lump of dough ferment and rise.

Leaven here symbolizes evil in the church, specifically the incestuous man (v. 1). God’s church must be unleavened or pure. Tolerating unrepentant sexual immorality ruins the whole church’s purity. Unchecked sin can quickly spread, like cholera or Ebola.

5:7b Paul adds a reason for his statement that “you really are unleavened.” The first line of verse 7 (“Cleanse out the old leaven”) alludes to Exodus 12:15, part of a passage in which God commands Israel to “kill their lambs” (Ex. 12:6). Here Paul argues that the church is already unleavened because “Christ, our Passover lamb, has been sacrificed.” “Passover lamb” translates pascha, which here refers to “Christ and his bloody death” (BDAG). Jesus is “the Lamb of God” (John 1:29, 36) who died on the cross as the Passover lamb (cf. John 19:31, 42).62

5:8 Because “Christ, our Passover lamb, has been sacrificed” (v. 7b), it follows that we should “celebrate the festival.” In what manner? Negatively, “not with the old leaven” (i.e., “malice and evil”), but, positively, “with the unleavened bread” (i.e., “sincerity and truth”).

Under the old covenant, Israel celebrated the festivals of Passover and Unleavened Bread together: Passover was a memorial on a single day, whereas the Festival of Unleavened Bread lasted a full week (Ex. 12:14–15). Under the new covenant, Jesus fulfills the Passover, and God’s people fulfill the Feast of Unleavened Bread. But now God’s people must continually celebrate the Festival of Unleavened Bread every day—not for just one week per year—by living in a holy way. When a church arrogantly tolerates leaven such as sexual immorality, it is celebrating that sacred festival with “malice and evil” rather than “sincerity and truth.”

5:9–11 Some Corinthians have (intentionally?) misunderstood Paul’s previous letter (cf. Introduction: Title). Paul does not mean that believers must not associate with unbelievers (i.e., those “of this world”) because it would then be virtually impossible to live on this earth (“you would need to go out of the world”). So Paul clarifies that believers must not closely associate with unrepentantly sinful people who profess to be believers (i.e., “anyone who bears the name of brother”). Granting such people Christian fellowship in the church is tolerating the old leaven of malice and evil (cf. vv. 6–8).

Paul names six sins in verse 11 (four of which he names in v. 10). Unrepentant sexual immorality is not the only sin that deserves church discipline. It is the sin that chapter 5 focuses on, but Paul includes a sampling of five other sins in verses 10–11:

(1–2)  “The greedy and swindlers” go together (and foreshadow what Paul addresses next in 6:1–11). They are so covetous that they defraud others.

(3)  “Idolaters” worship images or anything other than the one true God.

(4)  “Revilers” abuse others with their words, whether by slandering or by angrily bullying. When they criticize others, their words are not constructive but insultingly destructive.

(5)  “Drunkards” regularly get drunk and carouse. They are not self-controlled but alcohol-controlled. They are out of control.

This “vice list” is not exhaustive (cf. 6:9–10; Rom. 1:26–31; Gal. 5:19–21; etc.). Paul’s point is that if a sin so characterizes a professing believer’s life that he refuses to repent of that sin and others can label him by that sin (e.g., “Sarah is sexually immoral” or “John is a drunkard”), then the church must remove that person from among them (1 Cor. 5:2c).

Paul’s final line in verse 11 specifies what it means “not to associate with” such a person: “not even to eat with such a one.” At a minimum, this means the church should not let such a person celebrate the Lord’s Supper with them (cf. comments on 11:17–34). Further, what Paul prohibits applies to all meals in cultures in which sharing a private meal with such a person communicates to him or others that he is a genuine Christian (cf. Gal. 2:11–14). When a church member interacts with a former church member who has still not repented, the church member should not give the impression that all is well but should lovingly exhort the person to repent.

5:12–13 These four statements are corresponding reasons for verses 9–11. They occur in A-B-A'-B' form:

(A)  For what have I to do with judging outsiders?

(B)  Is it not those inside the church whom you are to judge?

(A')  God judges those outside.

(B')  “Purge the evil person from among you.”

The first and third lines support verses 9–10: God, not the church, is responsible to judge unbelievers (i.e., at this point in redemptive history; cf. 6:2). The second and fourth lines support verse 11: the church is responsible to judge professing believers among them.

The fourth line quotes nearly verbatim six passages from Deuteronomy in the Septuagint (Deut. 17:7; 19:19; 21:21; 22:21, 24; 24:7) and is very similar to three other passages (Deut. 13:5; 17:12; 22:22). In these contexts in Deuteronomy God commands the death penalty. Paul is certainly not advocating that churches execute those they remove from among them! God’s people under the old covenant were part of a theocracy, a geopolitical nation to whom God granted the authority to execute criminals. God’s people under the new covenant are not a theocracy. Paul quotes Deuteronomy because the principle undergirding God’s commands in Deuteronomy applies to church discipline under the new covenant. This principle is that because God and his people are holy, his holy people must remove from their community people who deliberately and unrepentantly disobey what God commands (1 Cor. 5:2c). They must cleanse out that old leaven (v. 7) and celebrate the festival without it (v. 8).63