B'rachos: To teach us that one can only acquire Eretz Yisrael trough hardship. ¹

B'rachos, 5a: It teaches us that one can only acquire Eretz Yisrael through Yisurim. ¹

Targum Yonasan: It is referring to its luscious fruit, which is also inherent in the other praises in the Pasuk. ¹

Ramban: Because on account of the numerous water sources - the streams, the fountains and the underground springs ¹ - that are found there, the land is akin to a satiated (watered) garden that does not require irrigation like Egypt does; ²

Seforno: Because Eretz Yisrael is a land of rivers, springs and underground wells, not canals and stagnant pools.

Targum Yonasan: It is referring to the clear water of its rivers, the sweet water of its springs and the fact that its underground water ³ never dries up.

Seforno: [The Torah writes "Eretz Tovah" twice, and another] five times "Eretz" S'tam because they refer to the five advantages that Eretz Yisrael has over other countries: 1. a land of good water-sources; ¹ 2. a land that produces its own food and 3. its own sweet delicacies; 4. a land where the currency is strong; 5. a land that contains strong building materials.

Da'as Zekenim, Hadar Zekenim and Rosh: They correspond to the seven nations.