King James Bible Dictionary

1. Heb. seor (Exodus 12:15, 19; 13:7; Leviticus 2:11), the remnant of dough from the preceding baking which had fermented and become acid.

2. Heb. hamets, properly "ferment." In Numbers 6:3, "vinegar of wine" is more correctly "fermented wine." In Exodus 13:7, the proper rendering would be, "Unfermented things [Heb. matstsoth] shall be consumed during the seven days; and there shall not be seen with thee fermented things [hamets], and there shall not be seen with thee leavened mass [seor] in all thy borders." The chemical definition of ferment or yeast is "a substance in a state of putrefaction, the atoms of which are in a continual motion."

The use of leaven was strictly forbidden in all offerings made to the Lord by fire (Leviticus 2:11; 7:12; 8:2; Numbers 6:15). Its secretly penetrating and diffusive power is referred to in 1 Corinthians 5:6. In this respect it is used to illustrate the growth of the kingdom of heaven both in the individual heart and in the world (Matthew 13:33). It is a figure also of corruptness and of perverseness of heart and life (Matthew 16:6, 11; Mark 8:15; 1 Corinthians 5:7, 8).

For bread
Exodus 12:34; Exodus 12:39; Hosea 7:4; Matthew 13:33

Leavened bread used:

With peace offering
Leviticus 7:13; Amos 4:5

With wave offering
Leviticus 23:15-17

Leavened bread forbidden:

With meat offerings
Leviticus 2:11; Leviticus 6:17; Leviticus 10:12; Exodus 23:18; Exodus 34:25

At the Passover
Exodus 12:19-20; Exodus 13:3-4; Exodus 13:7; Exodus 23:18

With blood
Exodus 23:18; Exodus 34:25

A type of sin
1 Corinthians 5:6-8

Figurative:

Figurative:
Matthew 16:6-12; Mark 8:15; Luke 12:1

Of other evils
1 Corinthians 5:6-8; Galatians 5:9

Parable of
Matthew 13:33; Luke 13:21

Various substances were known to have fermenting qualities; but the ordinary leaven consisted of a lump of old dough in a high state of fermentation, which was mixed into the mass of dough prepared for baking. The use of leaven was strictly forbidden in all offerings made to the Lord by fire. During the passover the Jews were commanded to put every particle of leaven from the house. The most prominent idea associated with leaven in connection with the corruption which it had undergone,a nd which it communicated to bread in the process of fermentation. It is to this property of leaven that our Saviour points when he speaks of the "leaven (i.e. the corrupt doctrine) of the Pharisees and of the Sadducees," (Matthew 16:6) and St. Paul, when he speaks of the "old leaven." (1 Corinthians 5:7) (Another quality in leaven is noticed in the Bible, namely, its secretly penetrating and diffusive power. In this respect it was emblematic of moral influence generally, whether good or bad; and hence our Saviour adopts it as illustrating the growth of the kingdom of heaven in the individual heart and in the world at large: because (1) its source is from without; (2) it is secret in its operation; (3) it spreads by contact of particle with particle; (4) it is widely diffusive, one particle of leaven being able to change any number of particles of flour; and because (5) it does not act like water, moistening a certain amount of flour, but is like a plant, changing the particles it comes in contact with into its own nature, with like propagating power.

ED.)

LEAVEN, noun lev'n. [Latin levo, Eng. to lift.]

1. A mass of sour dough, which, mixed with a larger quantity of dough or paste, produces fermentation in it and renders it light. During the seven days of the passover, no leaven was permitted to be in the houses of the Jews. Exodus 12:15.

2. Any thing which makes a general change in the mass. It generally means something which corrupts or depraves that with which it is mixed.

Beware of the leaven of the Pharisees and of the Sadducees. Matthew 16:6.

LEAVEN, verb transitive lev'n.

1. To excite fermentation in; to raise and make light, as dough or paste.

A little leaven leaveneth the whole lump. 1 Corinthians 5:6.

2. to taint; to imbue.

LEAVENED, participle passive lev'ened. Taised and made light by fermentation.

LEAVENING, participle present tense lev'ening. Making light by fermentation.

LEAVENING, noun lev'ening. that which leavens or makes light.

LEAVENOUS, adjective lev'enous. containing leaven; tainted.