Having taught "Ve'ahavta es Hashem Elokecha, why does the Torah see fit to add "Es Hashem Elokecha Tiyra"?
Ramban #1: To deter a person from sinning and getting punished.
Ramban #2: Refer to 6:5:3:2*.
Ramban #3: (citing Temurah, 3b): It is a warning against uttering the Name of Hashem in vain.
What do we learn from the word "Es Hashem Elokecha Tiyra"?
Torah Temimah #1 (citing Pesachim, 22a): It comes to include Talmidei-Chachamim. 1
See also Ba'al ha'Turim.
And what are the connotations of "Oso Sa'avod"?
Ramban #1: It means that one is obligated to serve Hashem like an Eved serves his master.
Ramban #3 (citing the Ibn Ezra): "Es Hashem Elokecha Tiyra" implies not to contravene Mitzvos Lo Sa'aseh, and "Oso Sa'avod", to keeping the Mitzvos Asei. 3
Ramban (citing the Sifri): Who comments on the Pasuk in Devarim 13:5 "ve'Oso Sa'avodu" - 'ba'Mikdash (See also Rashi there), incorporating Korbanos, Shir and Hashtachavayah, which all fall under the category of 'Avodah' - as the Torah indicates in Bamidbar 18:7 & 23.
Ramban, citing the same Sifri.
See Ramban's objection to this explanation.
Since when is it a Mitzvah to swear by Hashem's Name?
Rashi and Ramban #3 (citing Tanchuma): What the Pasuk means is 1 that if one has Yir'as Hashem 2 and one serves Him 3 (and one cleaves to Him - See 6:13:5:1) 4 , one is permitted to swear by His Name, otherwise not.
Ramban #1: The Pasuk means that one may only swear by the Name of Hashem, but not by the Name of any other god. 5
Ramban #2 (citing Temurah, 3b) and Targum Yonasan: The Pasuk is coming to permit swearing by Hashem's Name truthfully. 6
Ramban #4: Your Yir'as Shamayim will be so deep and you will be dedicated to His service 7 to such an extent, that you will always swear by His Name - even if it is to do something unpleasant - and abide by your oath.
Even though the two preceding statements in the Pasuk are Mitzvos - as the Ramban explains.
Ramban (Ibid.): Like Avraham, Yosef and Iyov, who are called 'Yir'ei Elokim.
Ramban (Ibid.): Someone whose only Avodah is that of Torah and Mitzvos.
Ramban: Someone who marries off his daughters to Talmidei-Chachamim, learns Chumash and Mishnayos, does business with Talmidei-Chachamim and benefits them from one's property.
Even if it is not for a Mitzvah - See Ramban.
Ramban: To the point that everything mundane act that you perform is to serve Hashem - See Ramban DH 'O Yomar'.
Why does the Pasuk insert "u'Bo Sidbak" in Eikev (Devarim 10:20) and omit it here?