Exodus 13:8-10

8And thou shalt inform thy son in that day, saying, It is because of what Jehovah did to me when I came out of Egypt.

9And it shall be for a sign to thee on thy hand, and for a memorial between thine eyes, that the law of Jehovah may be in thy mouth; for with a powerful hand hath Jehovah brought thee out of Egypt.

10And thou shalt keep this ordinance at its set time from year to year.