TSK · Exodus 23:18

They will eat the meat the same night; they will eat it roasted over the fire with bread made without yeast and with bitter herbs.

For seven days you must eat bread made without yeast. Surely on the first day you must put away yeast from your houses because anyone who eats bread made with yeast from the first day to the seventh day will be cut off from Israel.

Additional Grain Offering Regulations“‘No grain offering which you present to the LORD can be made with yeast, for you must not offer up in smoke any yeast or honey as a gift to the LORD.

The meat of his thanksgiving peace offering must be eaten on the day of his offering; he must not set any of it aside until morning.