Exodus 12:15; Exodus 12:16

15 For seven days you are to eat bread made without yeast. On the first day remove the yeast from your houses, for whoever eats anything with yeast in it from the first day through the seventh must be cut off from Israel.

16 On the first day hold a sacred assembly, and another one on the seventh day. Do no work at all on these days, except to prepare food for everyone to eat; that is all you may do.