1)
What is "Ye'areh"?
1.
Rashi: It is pouring. This is like "va'Temaher va'Te'ar Kadah" (Bereishis 24:20). Pouring applies to Ru'ach - "v'Shafachti Al Beis David? Ru'ach Chen" (Zecharyah 12:10), "Eshpoch Es Ruchi Al Kol Basar" (Yo'el 3:1).
2)
What Ru'ach will be poured?
1.
Radak: It is desire (Malbim - to save us). When Hashem will pour His desire on us, "the Midbar will be Karmel." Ru'ach is desire, like "El Asher Yihyeh Shamah ha'Ru'ach" (Yechezkel 1:12).
3)
How will the Midbar be Karmel?
1.
Radak: What is [now] Midbar will be Karmel - a place of seeded crops, grain fields and fruit trees.
4)
What is the meaning of "[veha'Karmel] la'Ya'ar Yechashev"?