What is the Feast of Unleavened Bread and why purge the leaven?

The Passover lamb is slaughtered on the fourteenth of Nisan. But the ordinance does not end there. Bound to it is a seven-day feast that extends through the fifteenth to the twenty-first of the month, and its demand is more sweeping than anything required of the Passover night itself: every trace of leaven must be removed from every house in Israel.

The Ordinance: Exodus 12:14–20

Exodus 12:14 names the day that began as the night of death: וְהָיָה הַיּוֹם הַזֶּה לָכֶם לְזִכָּרוֹן — "this day shall be for you a memorial" (H2146 זִכָּרוֹן, zikkaron, "memorial, remembrance," 24 occurrences). It is to be kept as a חַג ("pilgrimage feast") and a חֻקַּת עוֹלָם ("a statute forever"). The Passover is not a one-time event to be remembered privately; it is the fixed liturgical center of the Israelite year, the head of the calendar reset in Exodus 12:2.

The leaven law runs from verse 15 through verse 20. The core command: תַּשְׁבִּיתוּ שְּׂאֹר מִבָּתֵּיכֶם — "you shall put away leaven (שְׂאֹר, H7603, se'or, the active leavening agent, yeast) from your houses" (Exodus 12:15). The more general term is H2557 חָמֵץ (chametz, "anything leavened") — the finished leavened product. Both must go: neither the starter culture nor the bread it produces may remain. "No leaven shall be found in your houses for seven days" (Exodus 12:19). And the boundary is not national but residential: the rule binds the גֵּר (the resident alien) as fully as the native-born Israelite (Exodus 12:19). The shelter of the Passover is open to the stranger; its terms are not softened for anyone.

The bread eaten in place of leavened bread is H4682 מַצּוֹת (matzot, "unleavened bread"), a word that occurs 53 times across the canon. Deuteronomy 16:3 names it "the bread of affliction, for in haste (חִפָּזוֹן, H2649) you came out of Egypt" — the physical form of the bread encodes the experience of departure. The lamb was eaten in a posture of haste (Exodus 12:11); the bread that accompanies it is made without the time to let dough rise.

The Karet Penalty: Cut Off from the People

What distinguishes this feast from most Torah observances is the severity attached to its violation. Exodus 12:15 and 12:19 both carry the same sentence: כָּל אֹכֵל חָמֵץ וְנִכְרְתָה הַנֶּפֶשׁ הַהִוא מִיִּשְׂרָאֵל — "anyone who eats leavened bread, that soul (H5315 נֶפֶשׁ) shall be cut off (H3772 כָּרַת, Niphal) from Israel." This is the karet penalty — excision from the covenant community, the gravest communal sentence short of execution in the Torah. Within Exodus, the karet-of-the-soul formula falls in exactly three places: Exodus 12:15, Exodus 12:19, and Exodus 31:14 — the Sabbath. Passover observance and Sabbath observance stand as the two practices whose neglect or violation places a soul outside the covenant. Both mark the boundary of who belongs to Israel.

The seriousness is proportional to what the feast commemorates. The Passover was the night when the covenant God distinguished his people from Egypt by blood. To eat leavened bread during the feast of unleavened bread is not a dietary infraction; it is a refusal to embody the distinction — a symbolic alignment with the Egypt that was judged rather than with the Israel that was redeemed.

Ezekiel's Restored Temple Keeps It

Ezekiel's vision of the restored temple, the last extended prophecy in the Hebrew canon, preserves the Passover ordinance intact: "in the first month, on the fourteenth day of the month, you shall have the Passover (הַפָּסַח); a feast of seven days; unleavened bread (מַצּוֹת) shall be eaten" (Ezekiel 45:21). The same first-month dating, the same fourteenth-day slaughter, the same seven-day feast of unleavened bread. What was given in Egypt is still being observed in the prophet's ultimate vision of Israel's worship. The ordinance is not superseded by the entry into the land or the building of the temple; it outlasts both.

Paul Reads Along the Ordinance's Own Grain

First Corinthians 5:6–8 applies the leaven ordinance to the life of the church, and the logic follows directly from Exodus 12. Paul's situation: the Corinthian church is tolerating flagrant sin in its midst. His argument: ἐκκαθάρατε τὴν παλαιὰν ζύμην, ἵνα ἦτε νέον φύραμα, καθώς ἐστε ἄζυμοι — "cleanse out the old leaven, that you may be a new lump, as you are in fact unleavened" (1 Corinthians 5:7). The basis: "for Christ our Passover has been sacrificed" (1 Corinthians 5:7). The application: ἑορτάζωμεν ... ἐν ἀζύμοις εἰλικρινείας καὶ ἀληθείας, "let us keep the feast ... with the unleavened bread of sincerity and truth" (1 Corinthians 5:8). The Greek ἄζυμος (azymos) is the Septuagint's rendering of מַצָּה; ζύμη (zyme, "leaven") translates both H7603 שְׂאֹר and H2557 חָמֵץ.

Paul's logic mirrors the chapter exactly: because the Passover lamb has been slaughtered, live as the feast commands. The physical purge of leaven from the houses of Egypt becomes the moral posture of the church — the removal of the old life that belongs to the Egypt left behind. The feast of unleavened bread is not merely a memory of haste. It is the ongoing liturgical enactment of the distinction the blood created.