Exodus 12:14–20 and several other Old Testament passages tell us that once a year, in preparation for the yearly festivals of Passover and Unleavened Bread, the Israelites had to remove all leaven from their homes. Leaven was not pure yeast; instead, it was a bit of dough that was reserved when bread was baked as a starter for the next loaf. The first leavened loaf of bread made after Passover took longer to create because there was no leaven to start it. However, once that dough was leavened, one could take a piece of it to start leavening the next loaf. Then you would take a piece of dough from the second loaf to make the next one. This continued throughout the year until just before Passover, when all the leaven was discarded and a brand-new dough was started that had no part of what came before it.
This imagery forms the basis of the theological explanation for the excommunication of the man in the Corinthian church who was in a sexual relationship with his stepmother. His sin was like leaven that could contaminate everything, and purging him would heal the church and make it a new lump of dough like what the Jews worked with after Passover. This had to be done because, in reality, they were already the new lump of dough, an unleavened loaf, on account of the sacrifice of Christ, the true Passover Lamb (1 Cor. 5:6–7). Christ had removed the leaven of sin from them, so it could not be tolerated among them any longer. God in His wrath had passed over their transgression in the atoning death of Christ, with Jesus bearing the punishment for their sin in their place (Rom. 3:21–26). To tolerate sin would be, in effect, to pretend that the reality of His atonement and cleansing had never happened.
Of course, there is a broader application to Paul’s teaching, which he gives us in today’s passage. Christians cannot tolerate grievous sin in the community, but in a broader sense we must endeavor to cast out all sin (1 Cor. 5:8). We should not tolerate any malice or evil, but we should be open to reproof and correction, ever seeking to reform our lives and our congregations so that we become more and more what we already are in Christ—namely, holy.
As today’s passage tells us, we celebrate the reality of Christ’s Passover sacrifice by living in sincerity and truth. Let us not tolerate or excuse sin, but let us sincerely seek to form our lives and churches according to the doctrine and ethics of God’s Word.