Deuteronomy 16:3-4

CLV(i) 3 You shall not eat anything leavened with it. Seven days shall you eat unleavened cakes with it, the bread of humiliation (for in nervous haste you went forth from the country of Egypt), that you may remember the day of your going forth from the country of Egypt all the days of your life. 4 Let no yeast be seen with you in all your territory seven days. And let none of the flesh that you shall sacrifice in the evening on the first day lodge until morning.