Why does it say "b'Terem"?
Radak citing his father: Before this sign comes, the kings will depart.
Radak (16): Before he has Da'as to choose (when he begins to speak, about three years old, like other children), Shomron and Damesek will be desolate. The sign that the child will open his mouth to eat only what is sweet, will be from when he is born.
Which land will become desolate?
Rashi: The lands of Retzin and Pekach.
Radak citing his father: This land (Yehudah) will be desolate from them 1 ; they will leave. However, it is possible that they would return and conquer it - therefore he gave the sign of the youth, he will trust in Hashem; just like this sign was fulfilled, so will be fulfilled His word that they not conquer Yerushalayim. Their counsel will not last and will not be.
Radak: It says "Melacheha" - they were not the kings of Yerushalayim, rather, of Damesek and Shomron! This is because they considered themselves to be its kings.
What is the meaning of "Asher Atah Katz Mipnei Melacheha"?
Rashi: You are distressed and afraid due to the two kings, Retzin and Pekach. That year, Melech Ashur came against Damesek, for Achaz hired him, "va'Yispeseha va'Yagleha Kirah v'Es Retzin Hemis" (Melachim II, 16:9). And that year, Hoshe'a ben Elah conspired against Pekach ben Remalyahu, and struck and killed him in the 20th year from Yosam, which was the fourth year of Achaz.
Malbim: It is the land [of Retzin and Pekach] that you despise. [It will be desolate of its residents] due to the evil of its two kings.
