📖 Biblical Definition
Leaven was excluded from Passover (Ex 12:15) and from grain offerings (Lev 2:11), for its fermentation pictured corruption spreading through the whole lump. Jesus warned, "Watch and beware of the leaven of the Pharisees and the Sadducees... the leaven of hypocrisy" (Matt 16:6, Luke 12:1). Paul twice cites "a little leaven leavens the whole lump" (1 Cor 5:6, Gal 5:9) — small sins or errors spread through the whole body if unchecked. Remarkably, Jesus also compared the kingdom of heaven to leaven hidden in flour until the whole was leavened (Matt 13:33) — the only positive leaven-image in the Bible, and it is His kingdom working invisibly and unstoppably.
📜 Webster 1828 Definition
LEAV'EN, n.
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LEAV'EN, n. [Fr. levain.] A piece of fermented dough used to raise new dough. In Scripture, leaven is almost entirely negative: excluded from the Passover, forbidden in the grain offering, warned against as the leaven of the Pharisees' hypocrisy, and cited by Paul as the image of small sins that leaven the whole lump if unchecked. The one positive use is Jesus' comparison of the kingdom of heaven to leaven hidden in flour — invisible but unstoppable.
📖 Key Scripture
1 Corinthians 5:6-7 — "Your boasting is not good. Do you not know that a little leaven leavens the whole lump? Cleanse out the old leaven that you may be a new lump, as you really are unleavened."
Matthew 16:6 — "Watch and beware of the leaven of the Pharisees and Sadducees."
Matthew 13:33 — "He told them another parable. "The kingdom of heaven is like leaven that a woman took and hid in three measures of flour, till it was all leavened.""
Exodus 12:15 — "Seven days you shall eat unleavened bread... whoever eats what is leavened, from the first day until the seventh day, that person shall be cut off from Israel."
⚠️ Modern Corruption
Small sins spread invisibly. Small kingdom-leaven spreads invisibly. Scripture watches both.
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Paul says "cleanse out the old leaven" — specifically regarding tolerated sin in the Corinthian church. A little leaven does not stay little; fermentation pervades. Christians must watch for the leaven of hypocrisy, false teaching, and tolerated sin in their own lives and their churches. Dealt with quickly, it is a piece of dough; left alone, it pervades everything. The only good leaven is the kingdom itself.
🔗 Greek & Hebrew Roots
H7603 — se'or. G2219 — zymē.
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H7603 — se'or (שְׂאֹר) — leaven, yeast starter.
G2219 — zymē (ζύμη) — leaven.
Usage
"A little leaven leavens the whole lump. Small sin tolerated becomes the whole dough."
"The kingdom of heaven is leaven — invisible but unstoppable. The hidden work is not nothing."