What are "Pera'im"?
Metzudas Tziyon: They are wild donkeys.
What are "Shefayim"?
Rashi: They are streams.
Radak: They are high places. Pera'im stand there to see if there is grass anywhere. [It did not see any]; its only benefit [from ascending] was inhaling [fresh air]. It is a clear wind that goes unobstructed on mountains or in a wilderness. If a wind goes amidst settled areas, then houses, walls and fences block it. So the enemy will not be impeded. It will come just like it wants - with great masses, horses, cavalry, and splendorous dress.
Malbim: Wind can help (a) to clear clouds from the sky, and enable clear light [from the sun];(b) to winnow. A dry wind (when there are no clouds) does not do the former, and winnowing is not done in the mountains. Such a Ru'ach has no benefit. Also the Ru'ach of the false Nevi'im has no benefit! Nevu'ah of rebuke helps in the city, when people hear it. It separates the chaff from the grain (Resha'im from Tzadikim). And even when it is not heard, in the Midbar, it can clear the sky. People see what decree Hashem wrote about them above. The Ru'ach of the false Nevi'im does neither - it does not make people repent, nor does it tell the future.
What is the meaning of "Sha'afu Ru'ach"?
Refer to 2:24:4:1-2.
Why does our verse compare She'ifas Ru'ach to Tanim? Above (2:24), it does not do so!
Radak: The primary She'ifah is of Tanim. The Targum there says k'Yaroda.
Why does it say "Kalu Eineihem"?
Radak: When they saw that there is no grass, it is as if their eyes wore out from looking afar so much.
Why were they punished with such scarcity?
Radak: This was a punishment for their sins in settled places and in the Midbar. Other nations had satiation. This was a sign for the nations to receive punishment for their sins from Hashem - "v'Hayu Becha l'Os ul'Mofes" (Devarim 28:46).
