What is "Shever Al Shever"?
Rashi citing Targum Yerushalmi: It is Shever (downfall) Al (following) the exile of Yehoyachin.
Radak: First was the Shever of the [10] tribes, and now the Shever of Yehudah.
Malbim: We were already broken more than enough via the exiles. They saw that they cannot overcome the enemy, who succeeds unlike nature.
What is the meaning of "Nikra"?
Radak: This is like Mikreh (chance), even though it ends with an Aleph (and Mikreh ends with a Hei).
Why does it say "Pis'om Shudedu Ohalai"?
Radak: The esteemed houses and tall fortresses are called tents, for they were as easy to conquer as tents. They were plundered suddenly, in a moment.
Malbim: They were plundered suddenly, without preparation.
What is the meaning of "Rega Yeri'osai"?
Rashi: In a moment they plundered my curtains.
Radak: Refer to 4:20:3:1.
