Christian leaven

“Celebrate the Festival of Unleavened Bread, because it was on this very day that I brought your divisions out of Egypt. Celebrate this day as a lasting ordinance for the generations to come...”

(Ex. 12:17)

In reality, natural leaven does not belong either to the animal of the vegetable kingdom, but rather it is a fungus. It is a microscopic, unicellular fungus which produces enzymes capable of triggering the alcoholic fermentation of carbohydrates.

Nevertheless, despite it not being either an animal or a plant, our reason for focusing on it in this article is that it is mentioned 60 times in the Bible. Leaven and fermenting agents are classified as an ascomycete or basidiomycete fungus, which are characterised by the fact that they divide by means of a system known as gemmation. In the ovoid cell a little yoke appears which grows and finally separates from the mother cell. One of the most popular types of yeast is the Saccharomyces cerevisiae species, which is used for alcoholic fermentation and, therefore, for producing beer, wine, bread, antibiotics, etc.

The first historical references to the use of yeast to make bread come from ancient Egypt. It is supposed that some mixture of flour and water with natural contaminating agents might have accidentally fermented the dough before it was put in the oven, as a result of it having been left out more time than usual on a hot day. The result of this “domestic accident” was a loaf of bread which was lighter and more flavoursome than the usual hard cakes.

In Scripture, there are several Hebrew terms which refer to yeast and its effects. These are seor, which means “yeast” or “ferment” and appears five times in the Old Testament (Ex. 12:15, 19; 13:7; Lv. 2:11; Dt. 16:4). Another term is jamets, which is used to refer to bread with yeast or that has been fermented. On the other hand, there is another root, matstah, which indicates the opposite, “sweet” or “lacking yeast” (Lv. 10:12). Curiously, these different terms appear together in one verse: “Eat unleavened bread (matstsah) during those seven days; nothing with yeast in it is to be seen among you, nor shall any yeast (seor) be seen anywhere within your borders. (Ex. 13:7). The Hebrew word used for yeast (seor, שְׂאֹר), was translated as zyme in Greek and as fermentum in Latin.

The Hebrews considered yeast as a bitter substance capable of producing fermentation in bread dough. In fact, fermentation is the putrefaction of the organic matter, which releases into the air elements from that matter such as nitrogen, phosphorous and sulphur. Now we know that these elements can be used by plants in the unceasing cycle of matter in nature. However, in ancient times, this putrefaction had negative connotations from a religious point of view, and yeast was viewed as a symbol of moral corruption. Hence Jesus said to his disciples, “Beware of the yeast of the Pharisees and Sadducees” (Mt 6:6,11,12; Mk. 8:15; Lk. 12:1; 13:21; 1 Co. 5:5-8; Gal. 5:9), referring to the corrupt doctrine and hypocritical attitude of these religious authorities.

During the Jewish Passover, the Israelites did not use yeast to make bread because in this way they were reminded of their hurried escape from Egypt, when they did not have time to wait for the dough to rise (Ex. 12:11; Dt. 16:3). In the same way, the tasteless bread without yeast served as a reminder of the vicissitudes and afflictions that they endured during their slavery in Egypt, and later throughout their Exodus in the desert (Ex. 12:34, 39; Dt. 16:3; 1 Co. 5:7, 8). Likewise, yeast was forbidden in the offerings made to the Lord (Lv. 2:11; 6:17), as everything it touched spread to the whole offering, and was therefore therefore be contaminated by corruption, which was a symbol of the influence of evil in the world.

In the New Testament, the references to yeast are ambivalent. It most often is a negative symbol, while on some other occasions it is a positive one. It is often mentioned in the synoptic gospels to symbolise the evils of hypocrisy and doctrinal corruption on the part of the Pharisees or Sadducees (Mt. 13:33; 16:6, 11; Mk. 8:15; Lk. 12:1; 13:21). The apostle Paul refers to the believers’ need to cleanse themselves of the “old leaven” of sexual immorality in order to become the new unleavened dough in Christ (1 Co. 5:1-8). Likewise, with the old leaven of circumcision (Ga. 5:1-15), as “a little yeast leavens the whole dough”.

Nevertheless, in the parable of the yeast, it is actually used as a symbol for the kingdom of God (Mt 13:33) which is spreading slowly through the world; thus the emphasis is clearly positive. The kingdom of God is characterised in this way because, from its tiny beginnings a process was set in motion which has culminated in one of the most spectacular phenomena in human history. In this double parable, Jesus had the audacity to give the term a completely opposite meaning to the connotations that were familiar to his hearers. He even said to them that their thinking was mistaken because from something like a mustard seed, which they regarded as insignificant, and from a tiny pinch of yeast, which they had always thought of as a symbol of evil, the power of God was going to bring about his kingdom on earth. What you regard as evil, God has deemed good!

In the same way, the mustard seed becomes a leafy tree which gives shelter to birds, the miracle of divine love will convert this little flock into the people of God, who will proclaim salvation to all the peoples of the earth. Just as a few grams of yeast permeate and transform the lump of flour dough, a handful of insignificant men and women will go out and turn the world upside down!