1 Corinthians 5:6–8

1 Corinthians 5:6 — "Your boasting is not good. Don't you know that a little yeast leavens the whole lump?"

Paul has just addressed the Corinthian community's scandalous tolerance of a man living in an incestuous union with his father's wife (5:1–5). Rather than mourning and acting, the community was boasting — likely proud of their sophistication or their spirit of non-judgment. Paul turns this complacency on its head with a proverb that his readers would have recognized immediately: leaven (Greek zymē) was universally understood as a corrupting agent that works invisibly and pervasively through the whole batch of dough.

The image is both domestic and liturgical. In Greco-Roman culture leaven signified fermentation and moral corruption (cf. the later use in Gal 5:9). But Paul's primary frame here is Jewish and paschal: every devout Israelite knew that before Passover, every crumb of leaven was to be searched out and destroyed (Ex 12:15; 13:7). By invoking this image in the context of a specific moral failure tolerated by the congregation, Paul makes a pointed argument: the community's self-congratulation does not neutralize the corruption — it accelerates it. The sin of one member, left unrebuked, permeates the whole body.

1 Corinthians 5:7 — "Purge out the old yeast, that you may be a new lump, even as you are unleavened. For indeed Christ, our Passover, has been sacrificed in our place."

This verse contains one of Paul's most compressed and theologically explosive statements. The imperative "purge out" (ekkathairate) echoes the LXX language of ritual purification, specifically the Passover command to remove all leaven. The paradox Paul constructs is deliberate and profound: he tells the Corinthians to become what they already are — "even as you are unleavened." Baptism has already constituted them as a new, unleavened lump through incorporation into Christ. The moral command flows from, and must match, the ontological reality of their new status.

The pivot of the entire passage is the declaration: "Christ, our Passover (to pascha hēmōn), has been sacrificed." The Greek verb etythē ("has been sacrificed") is an aorist — a single, completed, unrepeatable act — with ongoing implications. Paul here identifies Christ as the true Paschal Lamb (Exodus 12), fulfilling every detail of the type: the unblemished lamb (Ex 12:5; cf. 1 Pet 1:19), the blood that marks and saves, the sacrifice at the appointed feast. This is not metaphor for Paul — it is the controlling typological reality that gives the Passover its deepest meaning. The old rite was always pointing forward to this event.

The phrase "in our place" (or "for us") carries substitutionary freight that Catholic tradition reads carefully: Christ's sacrifice is both sacrificial offering and redemptive act on behalf of the community.

1 Corinthians 5:8 — "Therefore let's keep the feast, not with old yeast, neither with the yeast of malice and wickedness, but with the unleavened bread of sincerity and truth."

The oun ("therefore") is crucial: the entire moral imperative rests on the theological indicative of v. 7. Because Christ has been sacrificed, we keep the feast. The Christian life is a continuous Passover celebration — a liturgical existence. The contrast Paul draws is sharp: "malice (kakia) and wickedness (ponēria)" versus "sincerity (eilikrineia) and truth (alētheia)." The first pair describes the festering, corrupting influence of unaddressed sin; the second pair describes a life transparent before God — grain untainted, bread baked without leaven, held up to the sun and found pure (a likely etymology of eilikrineia: eilē, sunlight + krinō, to judge).

Typologically, the passage moves through four senses: the literal Passover rite (historical), Christ as Passover lamb (allegorical/typological), the moral purification of the believer (tropological), and the eschatological feast of the Lamb (anagogical).

Catholic tradition uniquely illuminates this passage at the intersection of Christology, sacramental theology, and moral anthropology.

Christ as Paschal Lamb and the Eucharist: The Catechism teaches that "Christ our Passover has been sacrificed" (CCC 1340) is foundational to understanding the Eucharist itself. Paul's language is almost certainly eucharistic in resonance — he is writing near the time of Passover (5:7–8; cf. 16:8) and has already addressed the Eucharist in ch. 11. The Church Fathers were unambiguous: St. Cyril of Alexandria wrote that the true Passover lamb is Christ himself, and that "the shadow has given way to the truth." St. John Chrysostom (Hom. on 1 Cor. 15) sees the Corinthians' moral disorder as a desecration of the eucharistic feast they claim to celebrate.

The Indicative-Imperative Structure: The Council of Trent and subsequent Catholic moral theology affirm what Paul encodes here: grace is truly transformative, not merely imputational. The Corinthians are unleavened — baptismal grace has genuinely remade them — and therefore they must live accordingly. This structure refutes both a lax antinomianism ("grace covers all, so behavior doesn't matter") and a Pelagian moralism ("purge yourself by your own effort"). The purging is real, urgent, and necessary, but it flows from what Christ has already accomplished.

Leaven as Sin and the Church's Discipline: St. Augustine (Contra Faustum 12.16) reads the leaven of malice as pride — the very vice on display in Corinth's boasting — and connects it to the necessity of ecclesial discipline for the health of the whole Body. The Catechism affirms that sin wounds not only the individual but the ecclesial communion (CCC 1469), making Paul's corporate logic perennially relevant.

The Four Senses: Medieval exegetes, following Origen and Augustine, applied the four senses systematically to this passage. St. Thomas Aquinas (Super 1 Cor., lect. 3) identifies the literal sense (Passover rite), the allegorical (Christ the Lamb), the moral (purging vice), and the anagogical (the heavenly feast of Rev 19:9).

For contemporary Catholics, this passage confronts two comfortable illusions. The first is the illusion of spiritual compartmentalization — the belief that private sin, quietly tolerated, has no effect on one's family, parish, or community. Paul's leaven image insists otherwise: moral compromise is never fully private. A parent's casual dishonesty, a community's silence in the face of injustice, a parish's tolerance of factions and rivalry — these work through the whole lump. The second illusion is that sacramental participation is compatible with unexamined moral disorder. "Christ, our Passover, has been sacrificed" is not merely a beautiful doctrine; it is a summons to conformity of life.

Practically, Paul's rhythm of indicative-then-imperative offers a spiritually healthy structure for the examination of conscience: first, recall who you are in Christ — genuinely new, genuinely transformed through baptism and the Eucharist — and then examine your life against that identity. This grounds moral effort in gratitude and identity, not fear and performance. The question to bring to confession or daily prayer is not merely "what have I done wrong?" but "where is the old leaven I have not yet purged?"