NE of the most important & difficult things to maintain within a local congregation of saints is purity. Keeping ourselves unspotted from the world & untainted from the lusts of the flesh, the lusts of the eyes, & the pride of life – not easy. The church in Corinth wasn’t succeeding in this area. Sin had crept into that church, polluting their testimony. Paul called on them to judge themselves. Church discipline was needed.
Sexual misconduct (fornication) was common in this church (vs. 1). One might expect that true Christians wouldn't be tempted to seek for satisfaction from the false gods of sexual deviance. One would be wrong. While we do have a new nature, we also retain our old sinful nature (along with the body, which incases & sustains it). If we do not flee from unlawful sensual pleasures, we will succumb to their tantalizing appeal. The Corinthians did. And according to Paul, they were guilty of perversions that were not even accepted among the unsaved. They were tolerant of incest (vs. 1). That's hard for us to even imagine. But what may be harder for us to understand is how Paul didn't cut ties with the entire congregation. He simply pushed them to discipline their converted (yet perverted) members, so that corporately they could move toward a condition of holiness & purity.