Why does the Torah insert the word "Re'ei ... "?
Rashi: 'You can see with your own eyes! 1 I am not concocting it'.
Seforno: 'See, how the inhabitants of the land are too terrified of Yisrael to defend themselves.
Refer to 1:8:1:2 and to 1:21:1.5:1
What are the implications of "Bo'u u'Reshu es ha'Aretz"?
Rashi: It implies that the Cana'anim will all flee, and they will conquer the land without having to raise a sword. 1
Ramban: It implies that conquering Eretz Yisrael is (not a promise, but) a Mitzvah. 2
The Seforno also extrapolates from the words "Re'ei, Nasati lifneichem es ha'Aretz!" that the Cana'anim
Refer to Bamidbar, 33:53:1:1, 2.
Having said "la'Avoseichem", why does the Torah add "le'Avraham, le'Yitzchak u'le'Ya'akov"?