Radak: It will pass.

Malbim: First it will pass through Yehudah haphazardly, without making an impression at all.

Rashi: [It will flow] strongly.

Malbim: [Machaneh Ashur] will spread to the point that it washes away whatever it encounters.

Malbim: Afterwards, it will pass through regularly.

Rashi: Until the primary strength of their necks.

Rashi citing Targum Yonasan: Until they reach Yerushalayim. Radak - Yerushalayim is depicted as the head of the body. When water is up to a person's neck, he is close to drowning. If the water will rise slightly, it will pass his head and he will drown. So Melech Ashur, when he came to Yerushalayim, was like water that reached the neck. Yerushalayim was close to being captured, if not for Kel's mercy.

Malbim: After the river fixes where it will flow, the water will get deeper, until it reaches a person's neck; anyone who passes through is in great danger.

Rashi: They are small joints at the end of the wings. Tanchuma (Tazri'a 10) - just like Motos are one part in 60 of Kenafav, one part in 60 of Sancheriv's men would suffice for Eretz Yisrael (Radak - to fill the width of Eretz Yehudah).

Radak: This is like Montos; the Dagesh in the Tes is in place of the missing Nun. It is the Netiyah (leaning) of his camp and its spreading (Malbim - not only in depth, rather, also in width).

Rashi: It is Eretz Yehudah.

Malbim: It is Imanu'el's land; the verse speaks to him. It depicts the nation in this child. It attributes what occurs to the nation, i.e. Yehudah.

Rashi: Shevet Yehudah - Hashem promised them to be with them in the days of Chizkiyah, like the Nevi'ah ¹ who called her son Imanu'el.

Radak: It is Achaz' son. This is a sign that Yerushalayim will not be conquered. You, Imanu'el, are with us in Yerushalayim - via You, people will recognize that Kel is with us, for we will be saved from Melech Ashur. The rest of the land was full of them.