What exactly, is Hashem telling Moshe in this Pasuk and in the next one?
Rashi: He is telling him that, having appeared to the Avos with the Name Keil Shakai and made a covenant with them to save their children from the slavery and to take them to Eretz Cana'an, He was now obligated to fulfill it. 1
Seforno: He is telling him that, besides redeeming Yisrael in order to establish them as His people, Hashem also needed to do so to fulfill the covenant that He made with the Avos, and because He had heard Yisrael's cries and prayers from their troubles. 2
Seforno: Thus rendering them deserving that Hashem should remember His covenant, as the Pasuk indicates in Tehilim, 106:44,45.
Bearing in mind that the Avos were no longer alive, how can the Torah write "Laseis Lahem"?
Sanhedrin 90b: This is a proof (one of many) for Techiyas ha'Meisim Min ha'Torah.
Why did Hashem add the (otherwise superfluous) phrase, "Es Eretz Megureihem... "?
Oznayim la'Torah: To emphasize the fact that, despite Hashem's promise to give the Avos Eretz Cana'an, they remained sojourners all their lives - Avraham had to acquire a burial-site to bury Sarah, and Yaakov had to purchase a portion of field to pitch his tent. Yet they never complained the way that Moshe had just done. 'Chaval Al d'Abdin....' 1
The Pasuk implies that we merited the Land specifically in the merit of our Avos. What are the implications?
Maharal (Nesivos Olam, Nesiv Lev Tov, Ch. 1, p. 211): We would merit to remain in the Land, only so long as we act in the ways of the Avos! When we transgressed the ways of the Avos 1 by sinning in Giluy Arayos, Avodah Zarah, and Shefichus Damim, we were exiled from the Land (Yoma 9b, Avos 5:9). 2
Maharal (ibid.): Giluy Arayos is the opposite of Avraham's Midah, for he did not gaze even at his own wife Sarah (Bava Basra 16a). Avodah Zarah is in contrast to Yitzchak, who offered himself before Hashem. Shefichus Damim goes against Yaakov, who was the antithesis of (Esav's) bloodshed, and never even saw Keri - refer to Bereishis 49:3:2.1:1.
Maharal (Derech Chayim to Avos 5:9, p. 247): Yet in another sense, even the Avos developed their greatness due to the holiness of Eretz Yisrael.
QUESTIONS ON RASHI
Rashi writes: "'V'Gam Hakimosi...' - Even as I appeared to them by [the Name] Kel Shakai (6:3), I established a covenant...." What is Rashi inserting here?
Gur Aryeh: The opening word "Gam" (also) does not introduce a new idea (as in, 'And in addition, I established...'). Rather, it continues the idea that was begun by the preceding Pasuk (6:3) - 'When I promised by the Name Kel Shakai (and not by the Name Havayah), 1 I backed up My promise with a covenant....'
See Rashi to 6:3.
Rashi writes: "... Thus, I vowed, and have not (yet) fulfilled!" Where is this indicated in the Pasuk?
Gur Aryeh: What is written in the Pasuk, is that Hashem made a covenant with the Avos. It is obvious that He has not yet fulfilled - for the Bnei Yisrael were still in Egypt, and He had not yet redeemed them!
