Exodus 13:9

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. These are proverbial expressions denoting that the Israelites should keep the facts of their deliverance in their memories always, as the people of many nations wore bracelets and frontlets to remind them of certain religious duties. The redemption of the Lord and His ordinance concerning it was to be accepted with believing hearts and to be fulfilled with faithful hearts, with hearts conscious of the debt of gratitude which all Israelites owed to the Lord.