Leaven

Concept

Leaven (Hebrew seor; Greek zyme) was the fermenting agent used in bread-making, typically a piece of old dough preserved from a previous baking. Its pervasive, hidden action made it a powerful symbol in both directions. Leaven was strictly excluded from Israel's sacrifices and from all the Passover observance (Ex. 12:15; Lev. 2:11), symbolizing the removal of corruption and the urgency of the exodus. The entire Feast of Unleavened Bread reinforced this imagery over seven days. In the New Testament, Jesus uses leaven negatively as a symbol for corrupt teaching that spreads invisibly through the whole (Matt. 16:6–12; Luke 12:1) but also positively in the parable of the kingdom as the hidden transforming power that leavens the whole lump (Matt. 13:33). Paul employs both senses (1 Cor. 5:6–8; Gal. 5:9).