“Seven days you shall eat unleavened bread. On the first day you shall remove leaven from your houses, for whoever eats leavened bread from the first day until the seventh day shall be cut off from Israel. On the first day you shall hold a solemn assembly, and on the seventh day a solemn assembly. No work shall be done on those days. Only what everyone must eat, that alone may be prepared by you. You shall observe the feast of unleavened bread, for on this very day I brought your companies out of the land of Egypt. You shall observe this day, throughout your generations, as a perpetual ordinance. In the first month, from the evening of the fourteen day until the evening of the twenty-first day you shall eat unleavened bread. For seven days no leaven shall be found in your houses. For whoever eats what is leavened shall be cut off from the congregation of Israel, whether an alien or a native of the land. You shall eat nothing leavened. In all your settlements you shall eat unleavened bread.”
For seven days you would eat unleavened bread. On the first day, you had to remove all the leaven from your house. If you ate leavened bread during this time, you were cut off from Israel. There is a solemn assembly on the first and seventh day, when no work was done. However, you could prepare meals. This is another perpetual ordinance that takes place after Passover in the spring time, from the evening of the fourteen day until the evening of the twenty-first day.
Leaven and unleavened bread becomes a big deal. What is this leaven, and why leave it out? Leaven is some kind of yeast that makes bread rise and makes it fluffy. Apparently, it takes longer to make leaven bread since you cook it longer. This unleavened bread is some kind of flat bread. This controversy carried over to Christianity about the use of regular fluffy bread or unleavened flat wafers in the Eucharistic Communion.