What are the connotations of "al Yadecha"?
Hadar Zekenim: If his right hand is weaker, he puts it on that arm.
Menachos 37a: Others there learn this from "Yadi Yasdah Eretz v'Ymini" (Yeshayah, 48:13), or we learn "u'Kshartam" from "u'Chsavtam" - just like the right hand writes Tefilin, so it ties them (so they must be tied on the left arm). Targum Yonasan (Shemos, 13:9, from Sifri) learns from "Al Levavecha" that it is on the left arm (and not the hand).
As the Gemara in Menachos, 37a learns from the fact that the Pasuk in Eikev, 11:18 writes in the same Pasuk as the Mitzvah of Tefilin "Vesamtem es Devarai Eileh al L'vavchem".
Why does the Torah refer to the Tefilin Shel Rosh as "Totafos"?
Rashi (citing Sanhedrin, 4a): The word is made up of two foreign words - the Kaspian word 'Tat' and the African word 'Pas', both of which mean 'two' - hinting at the four Parshiyos in the Tefilin Shel Rosh. 1
And each is in its own box, which explains why it is written only about the Tefilin Shel Rosh, but not about the Tefilin Shel Yad.
Having taught the Mitzvah of Tefilin in Parshas Bo, why does the Torah repeat it here?
Ramban (on Pasuk 7): In order a. to add the obligation of tying the Tefilin to one's arm and b. to hint at the knot of the Tefilin - which the Chachamim learn from a Halachah le'Moshe mi'Sinai.
Tosfos (Sanhedrin 4b DH Tat): The Torah mentions Tefilin in four Parshiyos; these are what must be written in Tefilin.
What are the connotations of "Bein Einecha"?