What is the meaning of "Imdu Al Derachim u'Re'u"?
Radak: Omed b'Da'as (resolve) about the good path and the bad path, and see with your understanding. This is like Eliyahu told those who served Ba'al "why do you waver on both sides? If Hashem is Elokim, follow Him!" (Melachim I, 18:21) Now, Nevi'ei ha'Emes tell you to be chastised, repent and you will not be given over to the enemy. Nevi'ei ha'Sheker say that you are on a good path, do not veer from it; do not fear the [true] Nevi'im's prophecies of being given over to the enemy - you will have Shalom. Discern with your intellect, which is correct!
Malbim: A parable for this is one who strayed from the road and went to the side of the road, and he seeks the road. They tell him, what do you seek? If you stand on the road, you will see it! Why did you veer to the side? If you cannot recognize the path yourself, ask those who go on it, and they will tell you! So Yisrael, when they veered from Hashem's path, they seek the path of happiness. They invent new Mitzvos that Hashem did not command - [Yaravam] made a Chag "ba'Chodesh Asher Bada mi'Libo" (Melachim I, 12:33) - as if they seek Derech Hashem. [Yirmeyah] tells them, why do you seek the path? It is because you veered from the paved path of your fathers. Take the Sefer Torah - there you will see Derech Hashem that your fathers went in.
What is the meaning of "Sha'alu li'Nesivos Olam"?
Radak: This is like Moshe said "She'al Avicha v'Yagedecha" (Devarim 32:7). So Yirmeyah told them, ask the ways of the world, i.e. the old ways, of previous generations. You will find that one who went in the path of Emes, good came to him, and one who went in the path that the false Nevi'im lead you, evil came to him, for it was a false path. In these two ways - intellect or tradition - you can recognize the good path, and go in it!
Malbim: If you cannot recognize the proper path, and you do not know Toras Hashem, ask your prophets and Chachamim.
What is "Margo'a"?
Rashi: It is rest (Radak - and pleasantness) (Malbim - for the spiritual Nefesh.
What was the answer "Lo Nelech"?
Radak: We will not investigate the ways. What we are doing is good in our eyes.
Malbim: They do not see a new path due to error and lack of knowledge. Rather, they do not want to go in Derech Hashem - the path of Torah and fear.
