Who will be gathered?
Rashi: The Nochrim.
Why will they be gathered?
Rashi: It is for their evil, to gather the prisoner to the pit prepared for him, i.e. Gehinom for those who must go there.
Radak: The Nochrim will be like prisoners due to Yisrael. They will not be allowed to lift a hand or foot until they utterly lower themselves in front of Yisrael.
Malbim: They will be gathered to Yerushalayim for war. The verse compares this to gathering prisoners to a pit. They do not put them in the pit until judging whether they are liable or innocent. So they will be gathered to Yerushalayim for judgment.
Why does it say "v'Sugeru Al Masger"?
Rashi: These are the seven chambers of Gehinom.
Malbim: After Hashem judges the Nochrim to be liable, they will be locked in the pit.
What is the meaning of "ume'Rov Yamim Yipakedu"?
Rashi: Sins of many days will be paid on them (Malbim - for what they sinned against Hashem and His nation Yisrael). This is like ha'Kalir composed [in a Yotzer] 'l'Rov Yamim Lehimanos Lachshov Lahem Cheshbonos.'
Radak: This will be after many days. Every nation will return to its kingship, for after they were accustomed to lowliness for many days, they will not do evil again.
Radak citing his father: The verse refers to Yisrael. They will be in Galus for many days. They are locked among the Nochrim and Yishmael 1 . After many days in Galus, Hashem will have mercy on [Jews among] each nation and redeem them.
He mentions Yishmael separately, for they do not serve idolatry. (PF)
