How can people bind God’s Word on their hands, put it as a memorial between their eyes, and write it on the gates and doorposts of their houses (see Exod. 13:9; Deut. 6:8, 9)? From these commandments, several Jewish customs emerged. The first was the creation of a Tefillin, also called a phylactery, or a small, square black box with a long, flowing leather strap. The box contains four compartments with four Scriptures: Deuteronomy 6:4-9, Deuteronomy 11:13-21, Exodus 13:1-10, and Exodus 13:11-16. These verses are writ- ten by a scribe on a small kosher parchment with a special black ink.
The Tefillin have two boxes, each attached to the black leather straps: one is attached around the bicep about heart level and the other is attached above the forehead, but not lower than the hairline. The straps then wind around the fingers and around the arm. Two blessings are repeated as the Tefillin are placed on the bicep and the forehead. Most young Jewish men begin wearing the Tefillin just prior to their thirteenth birthday.
During the time of Christ, Torah-observant Jews wore phylacteries. Jesus, being Jewish and being raised in the synagogue, would have worn the phylactery. However, He rebuked certain Pharisees for enlarging the boxes to make themselves appear more spiritual than others and to be seen of men (see Matt. 23:5).
From Page 146 of the Perry Stone Hebraic Prophetic Old Testament Study Bible