What is the meaning of "l'Shamah Tihyeh b'Yom Tochachah"?
Rashi: When you will dispute with them 1 , they will be astounded and have no answer. Why? "B'Shivtei Yisrael Hodati [Torah] Ne'emanah", and they transgressed it.
Rashi citing Pesichah to Eichah Rabah 6: When Hashem will dispute with them, they will have nothing to say.
Radak citing Targum Yonasan: On the day of paying obligations.
Malbim: This is why they will separate from Malchus Efrayim, for it will be desolate on the day that Hashem set to rebuke them for their sins and pay them for their deeds.
Radak: It says Tihyeh (feminine), for it refers to Adas Efrayim.
What do we learn from "b'Shivtei Yisrael Hodati Ne'emanah"?
Rashi citing Pesichah to Eichah Rabah, 6: Via the Shevatim, I informed that the judgment is Emes. When the 10 tribes were exiled, Yehudah and Binyamin were not exiled. The 10 tribes said, this is because they are the children of His palace ? He showed favoritism! Heaven forbid, it is not so! Rather, Yehudah's measure for sin was not filled yet. Once they sinned, they were exiled. The 10 tribes heard that, and had no answer. They said, He is powerful; He is Emes; He did not show favoritism.
Radak: When I rebuked them in the Midbar, when all the Shevatim were like one, I informed them the Emes ? "Im b'Chukosai Telechu?", Im Tishme'u 1 , "v'Im Lo Sishme'u" (Vayikra 26:3, 14). Since they did not heed me, I will destroy their land and exile them from it.
There is no verse Im Tishme'u. In Shma it says "Im Shamo'a Tishme'u" (Devarim 11:13), but it is not in the Tochachah. Why would Radak cite it? Perhaps Im Tishme'u explains "Im b'Chukosai Telechu"; it is the opposite of "v'Im Lo Sishme'u." (PF)
