Sourdough which is kept over from one baking to another, in order to raise the new dough. Leaven was forbidden in the Hebrews during the seven days of the Passover, in memory of what their ancestors did when they went out of Egypt, they being then obliged to carry unleavened meal with them, and to make bread in haste, the Egyptians pressing them to be gone, Ex 12:15,19. They were very careful in cleansing their houses from it before this feast began, 1Co 5:6. God forbade either leaven or honey to be offered to him in his temple, Le 2:11. The pervading and transforming effect of leaven is used in illustration of the like influence on society, exerted by the purifying principles of the gospel, or by false doctrines and corrupt men, Mt 12:23; 16:6-12; 1Co 5:6-8.
(2.) Heb hamets, properly "ferment." In Nu 6:3, "vinegar of wine" is more correctly "fermented wine." In Ex 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 (Le 2:11; 7:12; 8:2; Nu 6:15). Its secretly penetrating and diffusive power is referred to in 1Co 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 (Mt 13:33). It is a figure also of corruptness and of perverseness of heart and life (Mt 16:6,11; Mr 8:15; 1Co 5:7-8).
seor. A lump of old dough in high fermentation. As making it and leavening bread with it took time, unleavened bread was used in sudden emergencies (Ge 18:6; 19:3). It was forbidden in all offerings to the Lord by fire (Le 2:11; 7:12). The Israelites on pain of death were to have none in their houses or in the land during Passover for seven days, from 14th Nisan (Ex 12:15,19,39; 13:7; 23:18; De 16:3-4). Salt was its opposite, and was never to be absent from the altar burnt offering, representing the incorruptible imperishableness of Jehovah's covenant. Honey as liable to ferment also was excluded from the altar burnt offerings. Leaven reminded Israel of the haste with which they fled from Egypt, and of their sufferings, which answer to the insipidity of unleavened bread, "the bread of affliction."
Its prominent symbolical meaning was, it is bred of corruption and corrupts the mass with which it is mixed. Hence it represents "malice" (the evil habit) and "wickedness" (evil coming out in word and deed) as opposed to "sincerity" and "truth" (1Co 5:7). The Jews searched with extreme care their houses, to purge out every particle of leaven. So Christians ought to search their hearts and purge out every corruption (Ps 139:23-24). It also symbolizes corrupt doctrine (Mt 16:6). Another quality is its secretly penetrating and diffusive influence: 1Co 5:6, "a little leaven leaveneth the whole lump," the influence of one sinner corrupts many (Ec 9:18); but in Ga 5:9 a little legalism mixed with the gospel corrupts its purity. Though elsewhere used in a bad sense, leaven in Mt 13:33 represents the gospel principle working silently "without observation" from within, until the whole is leavened, just as the mustard tree represents its diffusion externally; so "flesh," though usually in a bad sense, in Eze 11:19 is in a good sense.
The decomposition of social elements, accompanying and providentially preparing the way for the gospel, makes the image appropriate. Leaven was allowed to be offered in the firstfruits and tithes (De 26:2,12; 2Ch 31:5), the Pentecostal loaves (Le 23:15,17), and the peace offering (Le 7:13). See Le 2:11 "as an oblation of firstfruits ye shall offer them (leaven and honey) unto the Lord, but they shall not be burnt on the altar for a sweet savour." In Am 4:5 the leavened bread was "with the sacrifice of thanksgiving of the peace offerings," not with burnt offerings of animals on the altar. Perhaps however the command is ironical, "offer by burning (margin) a sacrifice ... with leaven" (which was forbidden), your very offerings being open insults to God.
The leaven both of OT and of NT may be assumed to have always consisted of a piece of fermented dough from a previous baking. There is no clear trace, even in the Mishna, of other sorts of leaven, such as the lees of wine or those enumerated by Pliny (Hist. Nat. xviii. 26). In ordinary cases, in the preparation of the household bread, the lump of dough, above referred to, was either broken down into the water in the kneading trough (see Bread) before the fresh flour was added, or it might be 'hid' in the latter and kneaded along with it, as in the parable, Mt 13:33. The bread made from dough thus prepared was 'leavened bread' (Ex 12:16 and oft.); cakes made from flour without the addition of leaven received the special name mazzoth, 'unleavened cakes,' which gave their name to' the feast of unleavened cakes' (Ex 23:15 = etc, English Version 'unleavened bread').
The prohibition of leavened bread during the continuance of this Feast, including the Passover, is probably another illustration of conservatism in ritual, the nomadic ancestors of the Hebrews, like the Bedouin of the present day, having made their bread without leaven. The further exclusion of leaven from the offerings placed upon the altar of Jahweh
This was early used in the fermentation of bread. As a symbol it is always used in scripture for the working of the human element, whether mind or flesh, in the things of God, and hence evil. It was strictly forbidden to be burnt in any offering made by fire (Le 2:11); but in the peace offering, besides the unleavened cakes and wafers, the offerer was to present leavened bread, which was to be eaten. Le 7:12-13; 23:17-18. Its presence here might seem to suggest an exception to the statement that leaven always signifies that form of evil; but it is not, for the peace offering typifies worship, and there, alas, the worshipper is not entirely free from indwelling sin. In the parable of 'the leaven hid in the meal,' it also represents the same evil, which in an insidious way permeates the mass with which it is mixed. The solemn words are added, "till the whole was leavened." Lu 13:20-21. It is only a too true similitude of the kingdom of God, for everywhere evil is spreading therein. In Mt 16:6-12 leaven is applied to the teaching of the Pharisees and Sadducees. In the church, leaven when discovered must be purged out, for "a little leaven leaveneth the whole lump," 1Co 5:6-8 but in the kingdom it is represented as working until all is leavened. Mt 13:33. It is then that the King will purge out from His kingdom all that offend and commit iniquity, and cast them into a furnace of fire.
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,"
and St. Paul, when he speaks of the "old leaven."
(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. The Hebrews were forbidden by the law to eat leavened bread, or a food with leaven in it, during the seven days of the passover, Ex 12:15-19; Le 2:11. They were very careful in purifying their houses from all leaven before this feast began. God forbad either leaven or honey to be offered to him in his temple; that is, in cakes or in any baked meats. But on other occasions they might offer leavened bread or honey. St. Paul, 1Co 5:7-8, expresses his desire that the faithful should celebrate the Christian passover with unleavened bread; which, figuratively, signifies sincerity and truth. In this he teaches us two things; first, that the law which obliged the Jews to a literal observance of the passover is no longer in force; and, secondly, that by unleavened bread, truth and purity of heart were denoted. The same Apostle alludes to the ceremony used at the passover, when he says, "A little leaven leaveneth the whole lump;" that is, a small portion of leaven, in a quantity of bread or paste, corrupts the whole, and renders it unclean. Our Saviour, in the Gospel, Mt 16:11, warns his Apostles to beware of the leaven of the Herodians and Pharisees; meaning their doctrines.