Whom does this address?
Radak: The Navi tells Yisrael 'listen to what Hashem told me.'
Malbim: Above (3:1), it says "Shim'u Na Roshei Yakov." Hashem wanted to dispute with Yisrael in front of them, and they will judge - "you should know the Mishpat!" They did not want to hear. Hashem tells them that Hashem chose other judges in place of them who will hear His claim ? the mountains and hills. He tells the Navi to wage Hashem's quarrel in front of them ? they will hear his voice!
What is the significance of the mountains and hills?
Rashi, Targum Yonasan: They refer to the Avos and Imahos, respectively. Radak ? they will hear what their descendants bestowed to Hashem.
Radak: This is like "Ha'azinu ha'Shamayim va'Adaberah v'Sishma ha'Aretz" (Devarim 32:1), "Shim'u Shamayim v'Ha'azini Eretz" (Yeshayah 1:2). The land heard all Hashem's words! The quarrel is Hashem's rebuke of Yisrael ? He did all good things for them, and they bestowed evil to Him.
R. Avraham ben Ramoch (Tehilim 121:1): Harim are the great officers.
Should they quarrel with the mountains and hills?
Radak: They should take their quarrel to them. "Es he'Harim" is like El he'Harim. Also "v'Har'ah Es ha'Kohen" (Vayikra 13:49) is like El ha'Kohen. Show your quarrel to them!
Malbim: Refer to 6:1:1:2.
