The sixth chapter of Deuteronomy contains some familiar words:
Hear, O Israel: The LORD our God is one LORD: And thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might. And these words, which I command thee this day, shall be in thine heart: And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up. And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes. And thou shalt write them upon the posts of thy house, and on thy gates. (Deuteronomy 6:4-9)
This text has influenced Jewish culture for centuries. To help us understand how the Jews interpreted one part in particular, The Dake Annotated Reference Bible offers the following note from page 235 of the Old Testament:
Whether the commands in v. 18; 6:8; Ex. 13:9, 16 concerning the binding of portions of the law on the hand and forehead were intended to be taken literally or figuratively has been a matter of dispute among commentators. The Jews have for ages attached to them a literal meaning. The passages they selected were Ex. 13:1-10, 11-16; Dt. 6:4-9; 11:13-21. Two kinds of phylacteries were used. The one for the arm was a strip of parchment on which these texts were written. It was enclosed in a small square case made of parchment or calfskin, and fastened with a long narrow leather strap to the inside of the arm, between the elbow and the shoulder. When the arm touched the body the law would thus be near the heart. The strap was carefully wound around the arm and fingers so that the ends came out by the tip of the middle finger. Sadducees wore phylacteries on the palm of the hand instead of the arm. The case for the forehead was divided into 4 cells with a parchment in each. It was fastened with leather straps to the forehead, between the eyes and near the roots of the hair. Phylacteries were worn only by men. The common people wore them only during prayer, but the Pharisees wore them continually and even enlarged them to call attention to their piety. They became badges of vanity and hypocrisy, sometimes being worn as amulets. This show of them was rebuked by Christ (Mt. 23:5).