Certainly, the first-century Corinthians who questioned Paul’s authority and thought it belonged to those gifted in “words of wisdom,” or fine rhetoric, behaved arrogantly. They were rejecting the divinely appointed source of authority and power—namely, the cross—and nothing could be more arrogant than to reject what God appoints (1 Cor. 1–4). Yet, this arrogance spilled over into other areas, as we see in today’s passage.
If the Corinthians could arrogantly reject the divinely revealed wisdom of the cross, it was no big leap for them to arrogantly reject what else God had revealed. First Corinthians 5:1–2 tells us that they did so by tolerating a particular kind of sexual immorality in the church—“a man has his father’s wife.” Of course, Scripture forbids all sexual immorality, which translates the Greek word porneia. First-century Jews such as Paul viewed this as any sexual activity outside of lawful, biblical marriage. In this case, the particular immorality in view is that a man in the Corinthian church is sleeping with his stepmother, for Paul is referencing Leviticus 18:8.
Paul is clearly aghast at this, for he remarks that this kind of sexual immorality was not tolerated even among the pagans. First-century pagans were notorious among the Jews for celebrating all kinds of sexual immorality. But there were some acts that even the gentile pagans would not tolerate, and sleeping with one’s stepmother was one of them. Interestingly, both the non-Christians and non-Jews could get this right. This fact helps us understand that although the fall has affected the moral discernment of all people, those who do not worship the one true God can and do get some of His ethical standards correct. But in any case, the Corinthians should have known better because even those outside the covenant community knew better. So, the Apostle’s response of abhorrence makes a lot of sense.
Instead of tolerating such grievous sin, the Corinthians should have mourned (5:2). Mourning for the destruction that sin causes is always right, but in cases of particularly heinous sin, casting that person out of the church when he does not repent is also appropriate (v. 2). Paul will make a theological case for this throughout the rest of 1 Corinthians 5. Let us conclude, however, that Paul’s teaching means that the church is not for all people without qualification. It is for those who have turned from sin to follow Christ.