In 1 Corinthians 5:1-13, Paul admonishes the Corinthians to discipline a member of their congregation for gross sexual immorality. The discipline is redemptive, not punitive (verse 5). In other words, it aims to reconcile the man to God and the church. It is also protective, however (verse 6). Its aim is to guard the congregation from falling into sin themselves.

Paul uses the imagery of Passover to explain the protective function of church discipline:

Your boasting is not good. Don’t you know that a little yeast works through the whole batch of dough? Get rid of the old yeast that you may be a new batch without yeast — as you really are. For Christ, our Passover lamb, has been sacrificed. Therefore let us keep the Festival, not with the old yeast, the yeast of malice and wickedness, but with bread without yeast, the bread of sincerity and truth (verses 6-8).

The NIV translates the Greek word zume as “yeast,” although it more accurately is “leaven.” Leavened bread is made like sourdough bread. You take a piece of last week’s dough (which has gone “sour”) and knead it into this week’s bread. Like yeast, leaven ferments the bread, making it lighter, and giving it a distinctive taste. Unlike yeast, leaven can pose a potential health hazard over time as old bacteria – sometimes unhealthy – gets kneaded into new bread.

Once a year, observant Jews in Paul’s day (as well as our own) celebrate Passover, which is also known as the Feast of Unleavened Bread. On that day, they eat lamb, bitter herbs, and unleavened bread (Exodus 12:1-10) in commemoration of the Lord delivering their ancestors from slavery in Egypt. For the week leading up to Passover, they remove all leaven from their homes and eat only unleavened bread (14:14-20). This is the spiritual meaning of Passover. Removing leaven from the home also serves, incidentally, a vital public health function by ridding the home of bacteria that may have grown harmful.

For Paul, a failure to discipline Christians who persistently engage in immoral acts – whether sexual or otherwise – is like leaven in bread. It ferments and contaminates the community. We say that a rotten apple spoils the bunch. The phrase “a little yeast works through the whole batch of dough” is a first-century idiomatic equivalent. Later in this letter, Paul writes, “Bad company corrupts good character” (1 Corinthians 15:33). A failure to discipline a persistently immoral Christian is a failure to protect the church from his leavening influence.

Not only that, it is a failure to live the life Christ died to make possible. In Paul’s prophetic imagination, Christ is “our Passover lamb.” His death and resurrection forgive us the guilt of sin but also destroy sin’s power over us. In Christ, each of us is “a new creation” (2 Corinthians 5:17). We therefore should live with “sincerity and truth” rather than “malice and wickedness.”

In other words, Christ calls us to live lives unleavened by sin’s influence.