What is the meaning of "va'Tachel Ru'ach Hashem"?
Radak #1: The spirit that he had in Machaneh Dan 1 began for him. Perhaps he confronted the enemy; the verses do not discuss it.
Radak #2: Yakov's prophecy began [be fulfilled] - "Yehi Dan Nachash Alei Derech" (Bereishis 49:17).
What is the meaning of "Lefa'amo"?
Rashi: He came there Lif'amim (at times).
Radak citing Targum Yonasan: A spirit of strength rested on him constantly.
Radak: It is to strengthen him. This is the opposite of the Nif'al and Hispa'el forms of this verb, which mean removing strength and breaking limbs, e.g. "Nif'amti v'Lo Adaber" (Tehilim 77:5), "va'Tipa'em Rucho" (Bereishis 41:8), "va'Tispa'em" (Daniel 2:1).
Radak citing Sotah 9b: Ru'ach of prophecy chimed in him like a bell.
Malbim: A spirit of strength rested on him from time to time.
Why does it say "b'Machaneh Dan"?
Radak: This is where Dan camped when they went to capture Layish. 1
Malbim: Tzar'ah and Eshta'ol are also the names of cities in Yehudah (15:33). The verse teaches that he was between the cities of Dan.
I.e. they first camped in the inheritance they received, near Yehudah in the south, before going to Layish in the north. Refer to Yehoshua 19:41:1:1,2 and the notes there. (PF)