What was his Ru'ach Hashem?
Rashi: He expounded "Ra'o Ra'isi Es Oni Ami" (Shemos 3:7) - even though I see that they will make an Egel, I see their affliction. I.e. whether they merit or are guilty, it is upon Hashem to save them!
Radak citing Targum Yonasan: He had a spirit of prophecy.
Radak: He had a spirit of strength; Hashem removed all fear from him. Targum Yonasan explained like this below (6:34, 11:29) regarding Gid'on and Yiftach.
Malbim: (a) It was a spirit of judgment and strength, to judge Yisrael and return them to Hashem's ways. (b) Since they returned to Hashem's true laws, he went to war and Hashem helped him.
What is the meaning of "va'Ta'az Yado"?
Metzudas David: He became strong to defeat [Kushan] every time.
