Chapter five contains some of the harshest words from Paul in any of his inspired letters. The reason had to do with a situation he found appalling: a Christian man was having an affair with his step-mother (1 Corinthians 5:1-5). Not only was this something that the surrounding pagan culture would apparently not even consider, rather than exercising discipline, the congregation actually applauded it! Paul was quick with his verdict. If they had not done anything about it by the time he arrived, Paul was excommunicate the man himself.
Although the congregation must have thought that they were showing their “tolerance” and “inclusiveness,” Paul used an analogy of bread and yeast (1 Corinthians 5:6-8). Like a tiny bit of yeast permeates the entire loaf of bread, so even a little sin can permeate a church, and this was not just a little sin. At the Passover, the Jews eat unleavened bread. Since Jesus was the ultimate Passover sacrifice, how could they tolerate any sin at all in their midst?
In an earlier letter Paul had told them to not associate with immoral people (1 Corinthians 5:9-13). They took this to mean they should keep away the immoral people outside the church but still love everyone and everything inside the congregation. Paul had to correct their thinking. It is impossible to dissociate with all immoral people, because we still have to function in this world. Instead, his command was with regard to those inside the church. Contrary to modern opinion, a congregation is to be in the business of “judging” each other, to help keep each other right before God. Blatantly unrepentant people are to be removed from the congregation until they repent.