Following this sublime path, we will proceed to interpret the passuk in this week’s parsha: “And it will be for you a sign on your hand and for a remembrance between your eyes, so that Hashem’s Torah may be in your mouth, for with a strong hand Hashem took you out of Egypt.” We will begin by clarifying which tefillin corresponds to Torah she’b’chsav and which corresponds to Torah she’b’al peh. It appears that we can prove that the shel yad corresponds to Torah she’b’chsav based on the exposition in the Gemara (Menachos 36b) that the tefillin shel yad should be donned on one’s left arm. Regarding this, Rabeinu Bachayei (end of parshas Bo) writes in the name of one of the kabbalists: The tefillin that are on the left (arm) correspond to the right, as it states (Devarim 33, 2): “From His right hand, He presented a fire of law to them. The source for this notion is found in the Ramban’s sefer HaEmunah V’HaBitachon (Chapter 22): It is worth commenting that the rationale for donning the tefillin shel yad on the left arm is because it corresponds to the right arm of HKB”H.
In other words, we were commanded to don the tefillin on our left arms, because HKB”H is facing us; thus, His right arm aligns with our left arm. To substantiate this claim, he cites the passuk above: "מימינו אש דת למו"—from His right hand, He presented a fire of law to them. Additionally, the Tikunei Zohar (Intro. 11b) learns from this passuk that Torah she’b’chsav was given with His right hand. Hence, we place the tefillin shel yad on the left arm, because it faces the right arm of HKB”H, so to speak, with which He gave Torah she’b’chsav.
This explains very nicely what the michaber writes concerning tefillin shel yad (O.C. 27, 8): It is the universal custom to wind it around the forearm six or seven times. The Magen Avraham (ibid. 13) writes in the name of the Arizal and the Shela that the minhag is to wind it around the forearm seven times. In keeping with this discussion, the reason being that Torah she’b’chsav is comprised of seven sefarim. This is based on an elucidation in the Gemara (Shabbas 115b) related to the passuk (Mishlei 9, 1): "חצבה עמודיה שבעה, אלו שבעה ספרי תורה"—”She has hewn out her seven pillars,” these represent the seven books of the Torah.
Rashi provides the following clarification. Since the two pesukim of "ויהי בנסוע" represent a separate book of the Torah, there are actually seven books of the Torah: (1) Sefer Bereishis, (2) Sefer Shemos, (3) Sefer Vayikra, (4) Sefer Bamidbar until "ויהי בנסוע", (5) the passage of "ויהי בנסוע", (6) the remainder of sefer Bamidbar after the passage of "ויהי בנסוע", and (7) Sefer Devarim.
