[f.]; an untranslatable term, translated as “phylacteries,” a “ritual object” that is a combination of two components: “Tefillin shel Yad”, Tefillin worn on the Arm, or Hand and Tefillin shel Rosh, Tefillin worn on the Head.
A Jewish boy begins to wear Tefillin when he becomes Bar Mitzvah. Both the “shel Yad” and the “shel Rosh” consist of black leather boxes, each containing the four Scriptural passages that command the observance of this Command.
The Tefillin shel Yad is set on the arm, opposite the heart, and the Tefillin shel Rosh is set upon the head, opposite the brain, to convey the idea that the feelings of one’s heart and the thoughts of one’s mind are all placed in the service of G-d.