Deuteronomy 6:7-8

You shall teach them diligently to your children [impressing God’s precepts on their minds and penetrating their hearts with His truths] and shall speak of them when you sit in your house and when you walk on the road and when you lie down and when you get up. And you shall bind them as a sign on your hand (forearm), and they shall be used as bands (frontals, frontlets) on your forehead.