What are the ramifications of "Es Shabsosai Tishmoru"? Why does the Pasuk insert it here?
Rashi #1 and Ramban: Refer to 26:1:1:1.
Rashi #2: Refer to 26:2:4:3.
Seforno: To teach that even at a time when we serve other nations, we are obligated to keep Shabbos, even though Shabbos commemorates freedom. 1
Moshav Zekenim citing Targum Yerushalmi: Guard My Shabbosos
See also Ba'al ha'Turim.
What are the ramifications of "u'Mikdashi Tira'u"?
Rashi #2: Refer to 26:2:4:2.
Seforno: It teaches us that we must treat the Batei Kenesiyos and the Batei Midrash 2 with awe.
Targum Yonasan: It means that when one goes to the Beis-Hamikdash, one should go with awe.
Why does the Torah mention specifically Avodah-Zarah, Shabbos and fear of the Mikdash?
Ramban #1: Because they are the most important Mitzvos, and the same applies to all the Mitzvos.
Ramban #2: Because they incorporate all the Mitzvos. 1
Moshav Zekenim, citing Yevamos 6b: Shabbos is put next to Mora Mikdash, to teach that the latter always applies, even after the Churban, just like Shabbos (about which it says "Os Hi l'Olam"
R. Bachye: Shabbos incorporates the Mitzvos Asei, and Mikdash, the Mitzvos Lo Sa'aseh (See also R. Chavel's footnotes).
Anyone who admits to idolatry, it is as if he denied the entire Torah (Rashi Bamidbar 15:22, from Yalkut Shimoni Re'eh 877)! All his Mitzvos are worth nothing (Ramban, ibid.)! Yuma 86b - Teshuvah for Aveiros of Misas Beis Din and Kares, brings Kaparah only after afflictions. If he observes Shabbos properly, he is pardoned without this (Taz, Reish OC 242). (Or, our Gemara does not discuss one who ascribes power to idolatry, rather, only one who serves like the generation of Enosh (he thinks that Hashem wants us to honor His servants
Why does the Torah add "Ani Hashem"?
Rashi #1: It means that Hashem is faithful to reward those who keep His Mitzvos.
Rashi #2 (in Shavu'os, 15b, citing the first Perek of Yevamos): This Pasuk teaches us that building the Beis-Hamikdash does not override Shabbos, 1 because Yisrael and the Beis-Hamikdash are obligated to honor Hashem.
Rashi: And Yom-Tov is included in Shabbos.