Or, because it (Eretz Yisrael) drinks rain water, but not irrigation water, it is, therefore, written (Devarim 8:7) "For the L-rd your G-d is bringing you to a good land, a land of streams of water."
Or, because it does drink irrigation water, but not snow-water, it is, therefore, written "From the rain of the heavens you will drink water." Let "water" not be written (i.e., it is superfluous). Why is it written? (To indicate) even snow-water. And thus is it written (Isaiah 55:10) "For as the rain and the snow descend from the heavens … and soaks the earth and makes it bring forth vegetation, etc.", and (Job 37:6) "For to the snow He says 'Descend to the earth, etc.'"