Will Melech Ashur come against Achaz?
Rashi: No. He will come against his son Chizkiyah 1 , who will rule after him. Because Chizkiyah was a Tzadik, the Navi did not call him Achaz' son.
Radak: Yes; refer to 7:17:2:1. Malbim - this was a punishment for not trusting in Hashem, and calling to Melech Ashur for salvation. This caused Melech Ashur to repeatedly come to destroy Yehudah!
After this, Rashi writes that he came also against Achaz! Perhaps the Dibur ha'Maschil is incorrect. Rashi explains that "Beis Avicha" refers to Chizkiyah; "Alecha v'Al Amecha" simply refers to Achaz and Yehudah. (PF)
What are "Yamim Asher Lo Va'u"?
Rashi: There were not such days from when Malchus Beis David was divided, and Efrayim departed from Yehudah. The days will be when the army of Melech Ashur comes. Even in those days, a miracle will be done for Yehudah. We find that first he came against Achaz - "va'Yavo Alav Tilgas Pilne'eser Melech Ashur va'Yatzar Lo v'Lo Chazako" (Divrei ha'Yamim II, 28:20), and the miracle was in the days of Chizkiyah.
