Passover is an opportune time to break with our past and start over as new creatures in Messiah. Passover is an annual reminder that we must leave the old culture behind. We are free from the past, and we need to set aside those things in our lives that continue to enslave us. After all, starting over is what it means to be born again.
The Hebrew word for unleavened bread is matzah (מצה). The Passover meal initiates an annual seven-day festival called the Feast of Unleavened Bread. Throughout the seven days of the festival, leavened grain products are completely forbidden. Instead the LORD commands us to eat unleavened bread throughout the seven days. The Torah calls the entire seven-day festival "The Festival of Unleavened Bread."
Matzah refers to a special type of flat, cracker-like bread. In order to be Passover matzah, the bread dough must be baked less than eighteen minutes after the flour is moistened with water. If the dough is not baked within eighteen minutes of being moistened, it begins to ferment from the naturally occurring leavening agents in the atmosphere.
The Torah explains the significance of unleavened matzah bread in that the children of Israel did not have time to let their bread rise before they had to leave Egypt. They were in such a hurry that they only had time to bake the dough before leaving. To commemorate the exodus, leaven is removed at Passover and unleavened matzah bread is eaten for seven days.
In ancient times, there were only two ways to leaven bread dough. One way was to mix the flour with water and let it stand until it began to ferment naturally. More typically, a small batch of already leavened starter dough left over from the previous day's batch was tossed in with the flour and water. The old culture of leaven in the starter dough quickly spread through the new batch of dough. As the saying goes, "A little leaven leavens the whole lump" (1 Corinthians 5:6). By means of this method, a single culture of leaven was passed on from loaf to loaf to loaf, day to day. This is how sourdough bread is still made today.
The commandment to remove all leaven prior to the festival makes this second method of leavening impossible. The starter dough would have to be disposed of prior to the festival because it is already leavened. This is the imagery that the Apostle Paul is referring to when he says, "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 Corinthians 5:7-8). The old starter-dough leaven represents our old way of life. It is sin, godlessness, bad company, bad habits and all the things that taint our lives. Like an old culture of leavened starter dough, those things continue to leaven our lives from day to day, conforming us to our past. Paul urges us to make a clean break with the old culture and to start over as a new batch, like unleavened bread.
When the children of Israel left Egypt, they were leaving behind their old culture. While in Egypt they had absorbed much of the wickedness and idolatry of Egyptian society. The unleavened bread symbolized a new beginning. They were starting over.