Exodus 13:9

6 Seven days thou shalt eat unleavened bread, and in the seventh day shall be a feast to the LORD.

7 Unleavened bread shall be eaten seven days; and there shall no leavened bread be seen with thee, neither shall there be leaven seen with thee in all thy quarters.

8 And thou shalt shew thy son in that day, saying, This is done because of that which the LORD did unto me when I came forth out of Egypt.

9 And it shall be for a sign unto thee upon thine hand, and for a memorial between thine eyes, that the LORD'S law may be in thy mouth: for with a strong hand hath the LORD brought thee out of Egypt.

10 Thou shalt therefore keep this ordinance in his season from year to year.

11 And it shall be when the LORD shall bring thee into the land of the Canaanites, as he sware unto thee and to thy fathers, and shall give it thee,

12 That thou shalt set apart unto the LORD all that openeth the matrix, and every firstling that cometh of a beast which thou hast; the males shall be the LORD'S.