Exodus 12:14-15

“This is a day to remember. Each year, from generation to generation, you must celebrate it as a special festival to the LORD. This is a law for all time. For seven days the bread you eat must be made without yeast. On the first day of the festival, remove every trace of yeast from your homes. Anyone who eats bread made with yeast during the seven days of the festival will be cut off from the community of Israel.