'Chetzyo' is specific. Why does it have the prefix Hei?
Radak: We find like this
Why does it say "El Mul"?
Radak: They were not on [top of] the mountains, rather, on the slope.
Where are Har Gerizim and Har Eival?
Radak, like R. Yehudah, Sotah 33ba: They are near Shechem.
Radak, like R. Elazar, Sotah 33b: They are close to the Jordan. 1
Radak, Hadar Zekenim (Devarim 27:4): The Yerushalmi says that according to R. Elazar, they made two mounds near the Yarden and called them Har Gerizim and Har Eival.
Why does it say "Levarech Es ha'Am Yisrael ba'Rishonah"?
Rashi (from Sotah 37a): This teaches that the Brachos are before the Kelalos.
Malbim: The Ibn Ezra (Devarim 27:14) holds that the Shevatim on Har Gerizim blessed, and the Leviyim cursed. It is as if it says 'Yisrael Levarech Es ha'Am ba'Rishonah.' 1 According to the [other] Meforshim, [that the Leviyim blessed and cursed], it is difficult why it says "ha'Am Yisrael."
This seems unlike the Trup, which reads ha'Am together with Yisrael. (PF)
What were the Brachos?
Rashi: They are inferred from the Kelalos, e.g. blessed is one who will not make an image.
Radak: They said the Brachos "v'Hayah Im Shamo'a
QUESTIONS ON RASHI
Rashi writes that the Brachos are before the Kelalos. In Bereishis (27:29), he writes that Yitzchak put the curse first (Orarecha Arur) and Bil'am put the Brachah first "Mevorchecha Varuch " (Bamidbar 24:9), because Tzadikim first suffer, and enjoy tranquility at the end. Bereishis Rabah (66:4) says that Yitzchak loved Yisrael, therefore he concluded with a Brachah, and oppositely, Bil'am concluded with a curse!
Refer to Bereishis 27:29:5:3,4, 27:29:152:2 and the note there.
