What is the significance of the borders of Eretz Yisrael that the Pasuk spells out here?
Rashi and Rashbam: From the Yam-Suf in the east
to the Mediterranean Sea in the west,
and from the Sinai Desert in the south to the River P'ras in the north.
Pesikta Zutresa: This will be in the future. We do not find that the borders of Eretz Yisrael are from the Midbar until the river, nor from Yam Suf until Yam Pelishtim.
What does the Torah mean when it writes "Ki Etein be'Yedchem Es Yoshvei ha'Aretz ... ve'Gerashtamo mi'Panecha"?
Seforno: Expelling the Kena'anim from the land lies in the hands of Yisrael. And Hashem is exhorting them here not to be lax in going about achieving it.
See Yehoshua, 18:3, how Yehoshua castigated them when they were lax (Seforno).