On what will Shiras Ha'azinu testify?
Rashi and Rashbam (in Pasuk 30): It will testify that Hashem warned Yisrael in advance as to what will happen to them if they negate the covenant that He made with them. 1
Seforno: Refer to 31:26:2:1.
Rashbam (in Pasuk 30): And they will know that they are being smitten because of their sins. See also Sifsei Chachamim.
What are the implications of "Ki Lo Sishachach mi'Pi Zar'o"?
Rashi #1: It is a promise that the Torah will never be completely forgotten from Yisrael.
Rashi #2 (in the original manuscript), Targum Onkelos and Targum Yonasan: The Shirah is an apt witness because it will never be forgotten from Yisrael. 1
Refer to Devarim, 30:19:1:1.
How will we reconcile the current Pasuk "Ki Lo Sishachach mi'Pi Zar'o" with the Pasuk in Amos, 8:12 "Yeshot'tu Levakesh D'var Hashem ve'Lo Yimtza'u" - implying there will come a time when Torah will be forgotten?
Shabbos, 132b: The Pasuk in Amos means that they will not find 'Mishnah Berurah and Halachah Berurah in one place - in other words, there will be Talmidei-Chachamim, but they will not be experts in Halachah.
Why did Hashem insert "Ki Yada'ati es Yitzro ... "?
Ramban: Now that Yisrael's stubbornness had been revealed in the desert, it is appropriate to present them with the Shirah, which refers to the sins that they will commit 1 as fact, 2 and not just in the form of a warning - 'If you sin, you will be punished!'
Seforno: Hashem is referring to the fact that they are not entering Eretz Yisrael in order to serve Him - which is the main objective of inheriting it, 3 but in order to enjoy its fruits. 4
Ramban: As the Navi writes in Yeshayah, 48:4, 5.
Ramban: Since the potential had become fact - similar to what Hashem said to Avraham after the Akeidah "Atah Yadati ki Yerei Elokim Atah" - Bereishis, 22:12.
Seforno: See Tehilim, 105:44, 45.
Seforno: With the evil results that follow, as stated in Devarim 32:15
