Why did he say "Mi Yiten..."?
Rashi: Let the day come close.
Radak: We should merit to see the salvation!
Why did he say "mi'Tziyon"?
Radak: It is the capitol of Malchus Yisrael, and [Hashem's] honor dwelled there. The salvation will come from there.
Malbim: David saw with Ru'ach ha'Kodesh the salvation from Sancheriv, which was from Tziyon.
What is the meaning of "b'Shuv"?
Radak #1: It is Po'el Yotzei (it acts on others), like b'Hashiv (when Hashem will return Yisrael).
Radak #2: It is when Hashem will give rest [to Yisrael], like "b'Shuvah va'Nachas Tivashe'un" (Yeshayah 30:15).
Malbim: At the time of the salvation from Sancheriv, Hashem returned the exile of His nation 1 .
I.e. other cities of Yehudah that Sancheriv had conquered. No one says that the 10 tribes returned then! (PF)
Why did he say "Yagel Yakov Yismach Yisrael"?
Radak: Now they are sad and mourning in exile.
