Did Hashem swear?
Radak: His word is His Shevu'ah. It endures like a Shevu'ah. "Im Lo" is an expression of a Shevu'ah, like one who says 'if will be so, will not be so.' Similarly, "Im Lo Batim Rabim l'Shamah Yihyu" (5:9), "Im Lo Shivisi v'Domamti" (Tehilim 131:2).
Malbim: Yes.
Why does it say "Ka'asher Dimisi"?
Rashi: As I intended to do to Ashur, so it was. You, Nebuchadnetzar, saw that the words of Yisrael's Nevi'im were fulfilled on Sancheriv.
Why does it say "Ken Haysah"?
Rashi: Like was prophesized about Sancheriv, so happened.
Radak, Targum Yonasan: So will be. Past tense is used in place of future (this is common in Nevu'ah).
What is the meaning of "Ya'atzti"?
Radak: Etzah is fixing a matter and clarifying it.
Malbim: Hashem's Etzah is the purpose of his deed; His Machshavah is the means to carry it out. The purpose of felling Ashur was lest it harm Yisrael; the means was in Har Tziyon. Via this, they saw Hashem's Gevurah and Hashgachah over His nation, and did not return against them again 1 .
To whom does he refer? Ashur's entire camp was wiped out, except for a few survivors. One of them Nebuchadnetzar, led Bavel against Yerushalayim! However, that was after the Nevu'ah that it will be destroyed, and Amon and Mo'av needed to persuade him (Sanhedrin 96b). (PF)
Why does it say "Hi Sakum"?
