What is the meaning of "Te'eval"?
Rashi: It will be destroyed.
Will the sky truly be dark?
Radak: This is a metaphor (exaggeration) for the great affliction, like I explained (2:32, 4:25).
What is the meaning of "Al Ki Dibarti Zamosi"?
Rashi: My intent that I said, I will full it.
Radak: What I spoke to the Nevi'im, as I intended, I did not retract until now, and I will not retract from it. So it will be; it is proper that the land be destroyed.
Malbim: When Hashem promises to do good, He truly wants to do so. His mouth and intent are united. He does not desire evil - "Lo Achpotz b'Mos ha'Mes" (Yechezkel 18:32). Evil decrees are only for the sake of another matter - through the punishment, the nation will repent. His words are unlike His intent - His mouth says to bring evil, and He thinks not to bring it, i.e. He wants the nation to repent, and He will not bring the evil. "Rega Adaber
Bamidbar 23:19. Refer to Bamidbar 23:19:151:1-3.
All of this is a mere metaphor. Time and change (even of intent) does not apply to Hashem! To people, who live through time and change, it seems that Hashem's intent changed. (PF)
At this time it was decreed without possibility of retraction. Initially, Hashem sent Yirmeyah to make Yisrael repent, to avoid the Churban! (PF)
Why does it say "v'Lo Ashuv"?
Rashi: I will not retract to have good intent for them.
Malbim (based on Eichah Rabah 4:17): He will not retract, for Churban ha'Aretz caused that He not finish off Yisrael in His anger. This decree was for good! It was said and intended without regret.
