Parashas Eikev · Passuk 11:18
Therefore impress these My words upon your very heart:gvery heart Lit. “heart and self.” bind them as a sign on your hand and let them serve as a symbol on your forehead,hsymbol on your forehead See notes on 6.8.
Torah Temimah points to Menachot 37b.
TT lemma: על לבבכם וקשרתם, מלמד שתהא שימה כנגד הלב, מכאן לתפילין של יד שמניחן בג (unit 3 of 3).
English: “On your heart and you shall bind them” teaches that the placement should be opposite the heart. From here: tefillin of the hand are placed on the height of the arm, so that the tefillah is opposite the heart, fulfilling “place these My words on your heart.”
Derash on the verse (Bavli sugya) — not a formal named middah of the 13
The Gemara uses this passuk in a sugya (proof, illustration, or dispute). Named as one of R' Yishmael’s 13 or R' Eliezer’s 32 only when that move is explicit.
The geometry of tefillin is derived from “on your heart”: the hand box sits where the heart is faced.