The church in Corinth had a problem and it wasn't subtle. A man was sleeping with his father's wife. But what really alarmed Paul was that the church was proud of how open minded they'd become about it (1 Corinthians 5:1 and 2). They'd mistaken tolerance for maturity.
His answer is one of the toughest in all his letters. The church was to put the man out, "that his spirit may be saved in the day of the Lord" (1 Corinthians 5:5). That wasn't rejection for its own sake. It was a severe mercy, meant to wake someone up before the compromise finished its work.
Yeast Doesn't Stay Put
Paul explains his urgency with a kitchen picture: "A little leaven leavens the whole lump" (1 Corinthians 5:6). Anyone who has baked bread knows yeast doesn't politely stay in its corner of the dough. Left alone, it works through everything.
That's what unaddressed, unrepentant sin does inside a community. It doesn't stay contained to one person. It spreads, it starts to feel normal, and eventually it reshapes what everybody considers acceptable.
Think of a quarantine. We don't isolate someone with a contagious illness because we've stopped caring about them. We do it because we know how contagion works and the health of everyone else matters too.
What Paul Isn't Saying
This isn't permission to shun every sinner in sight. Paul says outright that he isn't talking about people in the world, because we'd have to leave the planet to avoid them (1 Corinthians 5:9 and 10). He's talking about someone who carries the name of Christ and keeps living openly in sin without any intention of turning. The standard inside the family is different from how we treat our neighbors outside it.
Where I Land
The father of the prodigal son runs down the road to meet his boy while he's still a long way off. That's God's heart toward anyone willing to turn around. This post is about something different: what happens when someone isn't turning, and the community pretends not to notice because speaking up feels unkind.
I know I've done that. I've confused kindness with avoiding every hard conversation. But yeast doesn't ask permission, and compromise doesn't stay small just because we ignore it. Loving a person and loving the truth were never supposed to compete.