Why does the Torah insert "Vesamtem ... " here after the punishment of Galus?
What is the difference between "Al Levavchem" and "Al Nafshechem"?
Seforno: "Al Levavchem" means 'Reflect on them', and "Al Nafshechem" means 'perform them with goodwill'.
Rashi writes that we must wear Tefilin and affix Mezuzos even in Galus, lest the Mitzvos be new when we return. Mitzvos that do not depend on the land apply mid'Oraisa also in Chutz la'Aretz (Kidushin 36b)!
Moshav Zekenim: The Mitzvah of Mezuzos on gates of cities is only mid'Rabanan in Chutz la'Aretz. The Torah Mitzvah is only on your gates.
Kol Eliyahu, Divrei Eliyahu: There is a printing mistake. Initially, the text in Rashi said "Hei Tov, Ayin Mem." A scribe expanded this to say "Hanichu Tefilin Asu Mezuzos." Really, it stands for "Hafrishu Terumos Isru Ma'aseros", Mitzvos that depend on the land. They should be kept in Chutz la'Aretz, lest they be new when you return!