What is a "Nesher"?
Refer to Vayikra 11:13:151:1 and the note there.
What is the meaning of "Im Tagbi'ah ka'Nesher"?
Radak: If you will elevate the place of your dwelling like a Nesher, which flies higher than all [other] birds.
What is the meaning of "Sim"?
Radak: This is like Tasim (you will put). Also "Aleh...; u'Mus ba'Har" (Devarim 32:49-50) is like Tamus (you will die. It is not a command!)
Why does it say "v'Im Bein Kochavim Sim Kinecha"?
Yerushalmi Nedarim 3:8: In the future, Esav ha'Rasha will cover himself with his Talis and sit with the Tzadikim in Gan Eden. Hashem will drag him and expel him from there. Kochavim refers only to Tzadikim, like it says "u'Matzdkei ha'Rabim ka'Kochavim l'Olam va'Ed" (Daniel 12:3).
Malbim: Even if you will ascend among the stars, I tell you to put your nest there, so I will make you fall from there. If one falls from a low place, it is not so dangerous. I command you to put your nest among the stars, to increase your fall, like one who wants to make his enemy fall. He raises him to a high place, to make him fall from there to the valley and his neck-bone will break. This Nevu'ah will be fulfilled in the end of days. Malchus Edom will be elevated above, and Hashem will cast it down to Emek Yehoshafat.
