Deuteronomy 6:8

Thou shalt bind them for a sign upon thins hand - Is not this an allusion to an ancient and general custom observed in almost every part of the world? When a person wishes to remember a thing of importance, and is afraid to trust to the common operations of memory, he ties a knot on some part of his clothes, or a cord on his hand or finger, or places something out of its usual order, and in view, that his memory may be whetted to recollection, and his eye affect his heart. God, who knows how slow of heart we are to understand, graciously orders us to make use of every help, and through the means of things sensible, to rise to things spiritual.

And they shall be as frontlets - טטפת totaphoth seems to have the same meaning as phylacteries has in the New Testament; and for the meaning and description of these appendages to a Jew's dress and to his religion, see the notes on Exodus 13:9, and Matthew 23:5 (note), where a phylactery is particularly described.

By adopting and regulating customary usages (e. g. Egyptian) Moses provides at once a check on superstition and a means of keeping the Divine Law in memory. On the "frontlets," the "phylacteries" of the New Test. Matthew 23:5, see Exodus 13:16. On Deuteronomy 6:9; Deuteronomy 11:20 is based the Jewish usage of the mezuzah. This word denotes properly a door-post, as it is rendered here and in Exodus 12:7, Exodus 12:22; Exodus 21:6 etc. Among the Jews however, it is the name given to the square piece of parchment, inscribed with Deuteronomy 6:4-9; Deuteronomy 11:13-21, which is rolled up in a small cylinder of wood or metal, and affixed to the right-hand post of every door in a Jewish house. The pious Jew touches the mezuzah on each occasion of passing, or kisses his finger, and speaks Psalm 121:8 in the Hebrew language.

6:8 Thou shalt bind them - Thou shalt give all diligence, and use all means to keep them in thy remembrance, as men often bind something upon their hands, or put it before their eyes to prevent forgetfulness of a thing which they much desire to remember.