What is the comparison to dew?
Radak: This is the opposite of "v'Yevosh Mekoro" (13:15). Dew does not cease 1 . So Hashem's good will never cease from them. This will be in the future, when they return from Galus.
Ta'anis 3a: Dew was never held back, even when Eliyahu decreed that there will not be dew or rain!
What is the comparison to a rose?
Radak: Keneses Yisrael is compared to a rose - "Ani Chavatzeles ha'Sharon Shoshanas ha'Amakim; k'Shoshanah Bein ha'Chochim" (Shir ha'Shirim 2:1-2).
Malbim: There is a rose called Shoshanas Yericho. It is not rooted in the ground. The wind carries it to distant lands via Midbaros. It gets moist from dew, and sprouts and grows beautifully. This is a Mashal for Yisrael; the wind carries them from place to place. They are exiled and moved about. Hashem is the dew that revives them in their Galus. They sprout beautifully, like a rose.
What is the metaphor "va'Yach Sharashav ka'Levanon"?
Rashi: Yisrael's roots will succeed, like roots of trees of Levanon, which are great.
Radak: Do not say that a rose has no roots, and it is easily uprooted. [Yisrael] will be planted in their land like great trees of Levanon which have many strong roots; they cannot be uprooted from their place - "v'Lo Yinaseshu Od me'Al Admasam" (Amos 9:15). This is like "ha'Ba'im Yashresh Yakov" (Yeshayah 27:6). Va'Yach is like "u'Machah Al Kesef Yam Kineres Kedemah" (Bamidbar 34:11).
Malbim: Even though He struck the roots - initially they were rooted strongly in their land, like [trees of] Levanon - its cedars are rooted deeply - these roots were stricken, and uprooted from their place. They have no fixed place and root. Even so, (refer to 14:7:1:2).
