1 Corinthians 5:8

These verses sit in the middle of Paul’s rebuke in 1 Corinthians 5. A man in the church was living with “his father’s wife” (1 Corinthians 5:1), that is, his stepmother, and Paul has already told the church “to deliver such an one unto Satan” (1 Corinthians 5:5). The believers ought to have grieved over the sin and dealt with it. They were “puffed up” instead, pleased with themselves while it went on among them.

“Your glorying is not good.” The word for glorying, kaúchēma, means a boast. It can mean either the thing a person boasts of or the act of boasting, and it can be used in a good sense or a bad one. Here it is plainly bad. Paul leaves unstated what they were boasting in. It may have been their spiritual gifts, their freedom in Christ or their sense of being enlightened, and whatever it was, it blinded them to how serious the sin among them was.

The word for good, kalós, is the ordinary word for good. Paul’s few words are an understatement, and the Corinthians would have heard the weight in them. To boast while that sin went unjudged was badly wrong and spiritually dangerous. True glorying belongs to Christ and to the holiness he gives his people.

Corinth was a busy, wealthy port city with people from many lands, known for its immorality and for the worship of Aphrodite. Many of the believers were Gentiles who had come to Christ out of that city’s ways, and they still lived among them every day.

“Know ye not” is a question whose answer the Corinthians already know, and Paul asks it to make a firm statement. He quotes a well-known proverb, “a little leaven leaveneth the whole lump”, and he uses the same words in Galatians 5:9. Leaven, zýmē, is ferment or yeast, often a piece of soured dough kept back from an earlier batch. The lump, phýrama, is a mass of dough, and the verb “leaveneth”, zymóō, is the action of leaven working through it. Once a little is pressed into the dough, it spreads through every part of it, quietly and completely.

The little leaven is the one sin the church has left alone, and the whole lump is the whole congregation. Sin tolerated in one member affects the purity, health and witness of all the others. That is why Paul asks for such strong action in this chapter. He warns Timothy that false teaching spreads in the same way: “their word will eat as doth a canker” (2 Timothy 2:17). God called Israel to be a holy nation, set apart from the nations around it, and he calls the church to be just as distinct. A church that boasts while it shelters open sin has forgotten whose people it is.

“Purge out” translates ekkathaírō, made of ek, “out”, and kathaírō, “to cleanse”. It means to clean something out thoroughly, and Paul gives it as a command. The church must act deliberately to remove the corruption from its midst. The word “therefore” ties the command to the warning of verse 6: because leaven spreads, it has to go. In Corinth that meant the discipline Paul had just commanded for the unrepentant man.

The old leaven is the sin that marked their life before Christ, and here above all the immorality they had tolerated. The goal is “that ye may be a new lump”, a fresh batch of dough with none of the old leaven worked into it. That is what the church is in Christ, for “if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new” (2 Corinthians 5:17).

The last words of verse 7 give the reason for everything before them. They open with “For”, gar, and the “even” that follows adds weight: the Passover sacrifice has already been made. Páscha is the word for the Passover, the feast at which Israel killed a lamb in memory of their deliverance from slavery in Egypt. Paul calls Christ himself “our passover”, the Lamb that the whole feast pointed to. “Is sacrificed” is thýō, to sacrifice or slay as an offering, and its Greek form, etythē, speaks of a completed act. Christ has been slain once, and his atoning work is finished.

In Egypt the blood of the Passover lamb protected Israel from death. The blood of Jesus delivers all who believe from the penalty and the power of sin, as John the Baptist proclaimed: “Behold the Lamb of God, which taketh away the sin of the world” (John 1:29). His sacrifice fulfils the Passover and all the sacrifices before it. “By his own blood he entered in once into the holy place, having obtained eternal redemption for us” (Hebrews 9:12), and “now once in the end of the world hath he appeared to put away sin by the sacrifice of himself” (Hebrews 9:26). His blood will “purge your conscience from dead works to serve the living God” (Hebrews 9:14).

This is what makes the command to purge the leaven so fitting. The Lamb has been killed, so the feast has begun, and the house must be clear of leaven. Christ died to forgive each of his people and also to cleanse his church as a whole, for he “loved the church, and gave himself for it; That he might sanctify and cleanse it”, so that “it should be holy and without blemish” (Ephesians 5:25–27). When a church deals with the sin in its midst, it is acting on what Christ has already done for it.

“Therefore let us keep the feast.” Paul includes himself, and with “therefore” he draws the conclusion of all three verses. He names the leaven to be kept out of the feast twice. First comes the “old leaven”, the former way of life. Then comes “the leaven of malice and wickedness”. Malice is kakía, ill will and depravity in the heart, and wickedness is ponēría, evil that goes into action and does harm. Between them they cover sinful attitudes within and sinful deeds without.

The bread of the feast is “the unleavened bread of sincerity and truth”, where the word “bread” is supplied by the translators to complete the sense. Sincerity, eilikríneia, means clearness or purity, a character free from pretence, mixed motives and hidden aims. The word is often explained as something held up to the light of the sun and found pure. Truth, alḗtheia, means reality, integrity and agreement with the facts, and in Scripture it reaches to God’s revealed truth and the gospel itself. Jesus said, “I am the way, the truth, and the life” (John 14:6). A life of sincerity and truth is the same in private as in public, honest in word and deed, and shaped by what God has said.

These verses ask each of us to look honestly at our own hearts for the old leaven that lingers there: pride, complacency, unconfessed sin, or a compromise we have made our peace with. Malice and wickedness can work quietly in our thoughts, our words and our dealings with others. God calls us to put them away and to live with sincerity and truth, the same person in private as in public.

They speak to churches as well. A church that tolerates open, unrepented sin, whether out of a mistaken idea of grace, fear of confrontation or plain indifference, harms its own health and witness. Love for Christ and for one another means facing sin with both truth and grace, seeking repentance and restoration for the one who has fallen and purity for the whole body. That takes discernment and courage, and a love for God’s honour and for the good of our brothers and sisters.

The strength for all of this comes from the cross. We put away the leaven because Christ our passover has already been sacrificed for us and has already made us unleavened. You can look at your own sin plainly, since Christ has dealt with it, and you can pursue holiness gladly, as one who is keeping a feast.