1)
Why will they not be hungry or thirsty?
1.
Radak: On the way, Hashem will open for them springs and make sprout fruit trees. This is a miracle - "ki'Ymei Tzeischa me'Eretz Egypt Ar'enu Nifla'os" (Michah 7:15).
2.
Malbim: Hashem will lead them with mercy - where the sun does not beat down, and where water flows.
2)
What is "Sharav"?
1.
Rashi: It is heat. Radak - this is like "Achalni Chorev v'Kerach ba'Laylah" (Bereishis 31:40); the Targum is Sharve.
3)
What are "Mabu'ei"?
1.
Radak: The root is Nava (flowing). Wherever they will go in the Midbar, water will flow for them.
