1)
Who are "Mesan'ei Hashem"?
1.
Radak: The other nations.
2.
Malbim: They are those who deny Hashem's existence and Hashgachah.
2)
What will they deny?
1.
Radak: Due to fear of Yisrael, they will say that they did not harm Yisrael. This is like "v'Yikachashu Oyvecha Lach" (Devarim 33:29).
2.
Malbim: Refer to 81:16:1:2.
3)
What will be with them forever?
1.
Rashi: Their punishments "will be eternal."
2.
Radak: The time of [Yisrael's] Brachah that began to be good would be forever. It would not cease or change, if they would heed Hashem's voice.
3.
Malbim: Will come the time of their punishments, which will make them perish forever.
