The Torah commands in Parashat Va’et’hanan (Debarim 6:8), “U’kshartam Le’ot Al Yadecha, Ve’hayu Le’totafot Ben Enecha” – requiring that one bind on his arm and on his head certain sections of the Torah. This is, of course, what we refer to as Tefillin. The Sefer Ha’hinuch lists the obligation to wear Tefillin as two separate Misvot – one Misva to wear the Tefillin Shel Yad upon the arm, and a second Misva to wear the Tefillin Shel Rosh upon the head. These two Misvot are not interdependent, and thus one who has only one and not the other should wear the one he has. The specified four sections of the Torah are written on a single piece of parchment which is then rolled like a Sefer Torah, from the end to the beginning, and placed inside the box of the Tefillin Shel Yad. This box is tied to the arm with Resu’ot (straps). These four sections are: “Kadesh Li Kol Bechor” (Shemot 13:1-10); “Ve’haya Ki Yebi’acha” (Shemot 13:11-16); “Shema” (Debarim 6:4-9); and “Ve’haya Im Shamo’a” (Shemot 11:13-21). The box of the Tefillin Shel Yad is worn on the upper left arm, near the heart. To explain the reason for this Misva, the Sefer Ha’hinuch reiterates a point he had made earlier, that the human soul lives in a spiritually hostile environment, so-to-speak. It originates from the pure, pristine domain of the heavens, but then descends into a physical body, which is beset by various drives, impulses, desires and lures. This is analogous to somebody who comes to a dangerous neighborhood, and needs guards to protect him from the hostile people who live there. Our “guards,” the Sefer Ha’hinuch writes, are the various Misvot which serve to remind us of our obligations to Hashem. We are commanded to affix Sisit strings to our garments, place Mezuzot on our doors, and wear Tefillin on our arms and heads, to remind us of our devotion to G-d, and they help protect us from the lures of the Yeser Ha’ra (evil inclination). Of course, as the Sefer Ha’hinuch observes, even with all these reminders, we are still prone to sin, and people occasionally act wrongly. But without these reminders, we would be even more vulnerable, and more easily lured to sin, and so these Misvot help us in our lifelong struggle to maintain our commitment to G-d. Many of the Halachot relevant to the Misva of Tefillin have been handed down to us as a “Halacha Le’Moshe Mi’Sinai” – tradition taught to Moshe at Mount Sinai. For example, the Kesisa – the Tefillin box – must be perfectly square, as must the Titura – the base underneath the box. The stitching around the base of the Tefillin must also be square. The Tefillin Shel Rosh must have a symbol of the letter “Shin” on either side. The parchment must be wrapped in material – called a “Matlit” – before being inserted into the Tefillin box. A thread made from the hair of a kosher animal is used to wrap the outside of the parchment. The Tefillin box is similarly stitched together with sinews from a kosher animal. The base of the box of the Tefillin Shel Yad has an extension called the “Ma’abarta” through which the strap passes. The strap of the Tefillin Shel Rosh is tied in back in the shape of the letter “Dalet.” The Tefllin straps must be black. Tefillin should be prepared only by Jews. The strap of the Tefillin Shel Yad must be long enough to pass through the “Ma’abarta,” be tied in a shape resembling the letter “Yod” alongside the box, and then wrap around the arm and reach the middle finger, around which the strap is wrapped three times. The Sefer Ha’hinuch follows the opinion that one recites only one Beracha when putting on Tefillin – the Beracha of “Le’hani’ah Tefillin.” If one made an interruption in between the placing of the Tefillin Shel Yad and the placing of the Tefillin Shel Rosh, then he recites a second Beracha – “Al Misvat Tefillin” – when putting on the Tefillin Shel Rosh. Likewise, if, for whatever reason, one puts on the Tefillin Shel Rosh without the Tefillin Shel Yad, then he recites the Beracha of “Al Misvat