Which land should not fear?
Rashi: Eretz Yisrael - if you will repent.
Radak: The residents of Eretz Yisrael need not fear.
Malbim: "Adamah" refers also to a place that is not a grain field, rather, a place of trees, like I explained above (1:10). Had the salvation been for His great name the trees would not have returned, like I explained above (19). Rather, it was in the merit of Yisrael, therefore also the trees returned to give fruits, miraculously.
What is the significance of "Gili u'Smachi"?
Radak: This is opposed to "Chigru v'Sifdu... Heililu...; Kadeshu Tzom" (1:13-14).
Malbim: Gil is for a Chidush of a good matter that was not expected at all - "Ki Higdil Hashem La'asos."
What is the significance of "Ki Higdil Hashem La'asos"?
Radak: Hashem did great matters - as opposed to the locusts, which did great evils.
Malbim: This refers to destroyed trees returning to sprout, which is supernatural.
