Exodus 13:9

6 For seven days let your food be unleavened cakes; and on the seventh day there is to be a feast to the Lord.

7 Unleavened cakes are to be your food through all the seven days; let no leavened bread be seen among you, or any leaven, in any part of your land.

8 And you will say to your son in that day, It is because of what the Lord did for me when I came out of Egypt.

9 And this will be for a sign to you on your hand and for a mark on your brow, so that the law of the Lord may be in your mouth: for with a strong hand the Lord took you out of Egypt.

10 So let this order be kept, at the right time, from year to year.

11 And when the Lord takes you into the land of Canaan, as he made his oath to you and to your fathers, and gives it to you,

12 You are to put on one side for the Lord every mother's first male child, the first-fruit of her body, and the first young one of every beast; every male is holy to the Lord.