Why does the Torah use the double expression "Shamor Tishm'run"?
Rashi: The Torah is issuing a stern warning to take steps not to forget one's learning. 1
By constantly revising what one learnt. See also Ba'al ha'Turim.
What are the implications of "Shamor ... Le'ahavah es Hashem Elokeichem"?
Seforno: It implies that one should learn Torah in order to comprehend Hashem's Chasadim via which one comes to love Him.
What are the implications of "Laleches be'Chol Derachav"?
Rashi (citing Shabbos, 133b): 'Mah Hu Rachum, af Atah Rachum - Mah Hu Gomel Chasadim, Af Atah Tigmol Chasadim!' (Just as Hashem is merciful, so too, should you should be merciful; just as He bestows Chesed, so too should you ?). 1
Seforno: Refer to 11:22:2:1 - thereby creating the means to go in the ways in which He leads the world - Tzedakah and Mishpat.
Sifri (49): "Kol asher Yikra be'Shem Hashem Yimalet" (Yo'el 3:5). How can someone be called on Hashem's name? The answer is that, just as He is called 'Rachum', so too, should you be called 'Rachum'; just as He is called 'Chanun', so too, should you be called 'Chanun'. 2
See note on answer #3.
Lev Eliyahu (in Shemos, p.75): The Sifri does not say 'just as He is merciful, so too, should should you be mercciful' ? but 'just as He is called 'Rachum' and 'Chanun' - without limits, so too should you be Rachum and Chanun without limits (as much as is humanly possible). That is the difference between doing Chesed and loving Chesed.
How is it possible to cleave to Hashem, who is described as 'a Consuming Fire'?
Rashi: The Torah means that one should cleave to Talmidei-Chachamim and it will be considered as if one is cleaving to Hashem. 1
Ramban #1 (citing the Ibn Ezra): It means to love Hashem and to go in His ways in order to cleave to Him in the end. 2
Ramban #2: With reference to Avodah-Zarah, it entails constantly cleaving to Hashem in one's mind to the exclusion of all other deities.
Ramban #3: The Torah means that one's mind should constantly cleave to Hashem - to think about Him and about loving Him when one goes on one's way, when one lies down and when one gets up - to the point that even when one speaks to other people, one haas Him in mind. 3
Seforno: The Torah means that everything that one does (even one's mundane activities) should be in order to serve Hashem. 4
Targum Onkelos and Targum Yonasan: What the Torah means is that one should come close to the fear of Him.
Mesilas Yesharim #1 (Perek 1): Everything that can bring him close to Hashem, he pursues it, and whatever can block being close to Hashem, he flees from it, like from a fire.
Mesilas Yesharim #2 (Perek 19): 'Deveikus' means that a person cannot separate or budge from Him.
Kesuvos, 111b: Anyone who marries off his daughter to a Talmid-Chacham, who does business with a Talmid-Chacham or ho benefits a Talmid-Chacham from his property is considered as if he cleaved to the Shechinah. 5
