What is "ha'Devarim ha'Eileh" referring to? How does it connect to the previous Pasuk?
Rashi: It refers to Torah-study. 1 Through studying the Torah one comes to recognize Hakadosh-Baruch-Hu (and love Him) and to cling to His ways.
What are the connotations of "Al Levavecha"?
Seforno: One should straighten all one's deeds with that 1 in mind.
Targum Yonasan: 'The Mitzvos of Hashem ... should be engraved on the tablet of your hearts!'
What are the connotations of the word "ha'Yom"?
Rashi: It means that one should treat Hashem's Mitzvos like a new edict, that everybody is eager to read, and not like an old one, which one does not esteem. 1
Shulchan Aruch (OC 61:15): When reciting Keri'as Shma, one must pause after ha'Yom before saying Al Levavecha or (in the second paragraph) Le'ahavah, lest it sound like you must love Hashem only today. (Rather, you are commanded today to always love Hashem.)
And what are the connotations of "Al Levavecha"?