Did Bavel (the capitol) have more than one wall?
Radak: Yes - there was an inner wall, and a thick outer wall. Their strength will not help; each 1 will be destroyed.
This explains why it says "Ar'er" (singular). (PF)
What is the meaning of "Ar'er Tis'ar'ar"?
Rashi: [They 1 are] expressions of digging, like "Aru Aru Ad ha'Yesod" (Tehilim 137:7).
Radak: They are expressions of breakage and demolition. This is like "Oreru Armenoseha" (Yeshayah 23:13). The root is Ohr; the middle letter of the root is not pronounced (as a consonant), and the first and last letters of the root are doubled. This is like "va'Tischalchal ha'Malkah" (Esther 4:4) from the root Chil.
Rashi discussed only Tis'ar'ar, but surely the same applies to Ar'er, especially since it is closer to "Aru", from which Rashi learns! (PF)
What is the meaning of "ba'Esh Yitzatu"?
Radak: They will burn in fire.
What is the grammatical form of "va'Yig'u"?
Radak: (It is from the root Yaga.) The Yud of the root is omitted. The Yud due to the conjugation has a Meseg (a minor accent, indicated via a line under it) due to the omission of the first letter of the root.
What is "Bedei Rik"?
Rashi: It is great emptiness that will come upon them. Radak - this is like b'Rik. Also Bedei Esh is like b'Esh. The word Dei is added to show that it is constant and great. The same applies to Bedei Shofar and Bedei Arbeh, due to their multitude.
Which nations are discussed, and what does the verse teach about them?
Radak: The nations in Bavel - if they will toil to save themselves, they toil in vain, for their salvation will be in fire. What they think will save them, it will come to them in fire and burn them. Their toil was in vain!
Radak #2: [Those who built Bavel] will recognize that their toil was in vain. The end of their toil will be [burned in] fire - "She'areha ha'Gevohim ba'Esh Yitzatu."
Malbim: They will toil to stand up the wall, and to extinguish the fire - but they cannot save.
