The Imagery of Leaven

by Lois Tverberg

Many of the images in the Bible are obvious to us. We understand God as a shepherd, or being under the protection of his wings.

One image that is not readily apparent is that of leaven, at least in the modern world. The regulation that for one week each year all leavening had to be removed from dwellings of the Israelites can baffle Western Christians. What is so negative about the little packets of yeast that we use in bread?

It seems especially odd that to celebrate Passover and the week after, during the Feast of Unleavened Bread, it was so necessary to live without yeast. This prohibition is still observed by Jews even until this day.

Learning about food preservation and bread-making in ancient times can help us better understand this imagery. Whenever grain or flour is allowed to get moist, it will acquire a sour taste and get moldy within a few days: the normal process of decay.

This process comes from yeasts and molds in the air that start growing and producing acids. The microbes will also produce carbon dioxide and sometimes alcohol in this process of fermentation. Without steps taken to prevent it, this will always occur over time.

Far back in ancient history someone discovered that at an early point in the process, when the dough is still edible, it can be baked and the acid and bubbles will add texture and flavor to the bread. It normally takes a few days before fermenting and rising occur naturally, but it can be greatly hastened by inoculating the lump of dough with a little of an old lump that has been aging longer.

The tradition started to take out a lump of dough made each day and keep it until the next day, and add to the next batch. Sourdough breads today are still made this way by adding a “starter” dough from an earlier batch. The lump of old dough would become sour and inedible overnight, and if left longer it would become rancid and rotten, but it would be mixed into the new lump of dough to cause it to rise.

Once we see this picture of ancient bread-making, it becomes much more obvious why leavened dough (hametz in Hebrew) became an image of a life contaminated by sin. The decay that would lead to “death” or rottenness was added to each batch.

Without it the dough tends to be sweet, but adding it would give the dough a slightly sour taste that would get stronger and stronger until it was baked. (Ancient breads probably tasted more like sourdough bread.) Think of how sin tends to “sour” our personalities, and also cause us to “puff up” with pride. Eventually, as Adam first found out, sin leads to our decay and death.

Interestingly, we find a motif that seems like original sin: the infection was started in the first lump of dough that was leavened long time ago, like Adam committing the first sin. Each lump of dough after that received its “decay” from the dough made the day before, like sin being transmitted from generation to generation.

Most of the time leaven is a negative image, and Jesus uses it that way when he says “Beware of the leaven of the Pharisees and Sadducees” (Matt 16:6). One time, however, he transformed the image to use it in a positive way, to describe the kingdom of heaven. He says that the kingdom of heaven is like leaven, because you can put a very small amount of leavened dough into a very large mass, and it will have a potent effect on the whole thing (Matt 13:33). 

Jesus was describing the powerful effect of the gospel, how even a few faithful believers can transform the world around them. Here he isn’t really referring to the image of decay but the ability of a very small amount of dough to cause a transformation of the whole dough. May we be like leaven in this way!

It’s good to think about what God was saying through leaven, especially around the time of Passover and Easter/Resurrection Day. The most powerful image of leaven is in the Passover meal that Jesus celebrates with his disciples as the Last Supper. When Jesus holds up the bread and says “This is my body” he certainly would have been holding up unleavened bread, or matzah, because the Jews were required to eat the Passover meal with unleavened bread (Deut 16:1-3).

Jesus wasn’t just speaking about his body as bread in general, but as this specific kind of bread, made without leaven, unadulterated by decay. Unlike the rest of humanity, who had been leavened with sin inherited from their fathers, he had not been infected with the “rottenness” that was in the rest of mankind.

By using this image he is saying another thing about himself: that he was fit as a sacrifice because he was free of leaven. All animal sacrifices offered up to God had to be without blemish, and any grain offerings offered up to the Lord by fire had to be free of leaven (Lev. 2:11, 6:17). It seems that when God prohibited his people 1,500 years earlier from eating leaven during Passover, he was thinking ahead to when Jesus would use the bread at the Passover meal to describe himself.

Because he is not leavened with sin, he is a suitable sacrifice, and because he is not infected with decay, he is God’s Holy One who will not see decay and will live on eternally! (Psalm 16:10, Psalm 49:9, Acts 13:34-37).

Paul and the other early Jewish believers understood this picture of leaven. Paul uses this image along with the fact that Passover came on the first day of the seven-day Feast of Unleavened Bread to describe how Jesus’ sacrifice should enable us to live righteously:

Do you not know that a little leaven leavens the whole lump of dough? Clean out the old leaven so that you may be a new lump, just as you are in fact unleavened. For Christ our Passover also has been sacrificed. Therefore let us celebrate the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth. (1 Cor 5:6-8)

May we all live transformed, unleavened lives!