Why does it say "Ki Cho Amar Hashem"?
Malbim: The evil coming upon you is not from the Ma'arachah, rather, from Hashem.
What is "Kole'a"?
Rashi: It is like one who shoots a rock from a slingshot. Radak - so each nation will be cast from its place, not only Yisrael. Therefore, [the nations] should not speak [lowly] about Yisrael. So Yirmeyah prophesized about Edom and Mo'av (49:7, 48:1), and also the others.
Malbim: I will cast [Yisrael] in a slingshot, far from their place.
Why does it say "ba'Pa'am ha'Zos"?
Radak: All nations will be stricken by Nebuchadnetzar, and afterwards Bavel, at the beginning of his grandson's kingship.
What is the meaning of "Lema'an Yimtza'u"?
Rashi, Targum Yonasan: They will get the 'payment' (punishment) for their deeds.
Radak: What I spoke to the Nevi'im will be fulfilled, so all will know that it is from Me.
Radak citing Ibn Ezra: Hashem will bring against them slingshot shooters, and the place will be confined for them. Since they are gathered [densely] together, the shooters will find (strike) them.
Radak citing his father: This is connected to the coming verse. Afflictions will find them, until each will say "woe to me for my breakage"; Yisrael are stricken.
Malbim: It is so they will [seek Hashem amidst their affliction, and] find Him - "v'Hefitz Hashem Eschem ba'Amim...; u'Vikashtem mi'Sham Es Hashem Elokecha u'Matzasa" (Devarim 4:27, 29).
