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
Such as through constant revision. 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 understand His Chasadim via which one comes to love Him.
What are the implications of "Laleches be'Chol Derachav"?
Rashi (from Shabbos 133b): 'Mah Hu Rachum, af Atah Rachum - Hu Gomel Chasadim, ve'Atah Tigmol Chasadim!' 1 (Just like He is merciful, also you should be merciful; just like He bestows Chesed, also you
How is it possible to cleave to Hakadosh-Baruch-Hu, who is described as 'a Consuming Fire'?
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. 3
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's mind is with Hashem. 4
Seforno: It means that everything that one does (even one's mundane activities) should be in order to serve Hashem. 5
Targum Onkelos and Targum Yonasan: What the Torah means is that one should come close to Hashem to fear Him.
Mesilas Yesharim Perek 19: Devekus means that a person cannot separate or budge from Him.