What is the command "Hismahmehu"?
Rashi: Deliberate to contemplate and think about your deeds.
Radak: This Nevu'ah was in the days of Achaz. It was said to Anshei Yehudah. Dleay; this is like "va'Yismahmah" (Bereishis 19:16). Think for a while, and contemplate the matter. How did this evil occur to you, that you abandoned Hashem's word that the true Nevi'im tell you, and the false Nevi'im entice you?!
Malbim: It is not a command. It discusses Bnei Yehudah who come in the morning to see the fall of Sancheriv. Initially they will hesitate to approach the fallen camp.
What is the command "u'Smahu"?
Rashi: Be astounded at your ruin.
Malbim: It is not a command. Bnei Yehudah who come to see the fall of Sancheriv will not believe what they see.
What is "Hishta'ash'u va'Sho'u "?
Rashi: It is like "v'Einav Hasha" (6:10); they were blind and unable to see.
Radak citing his father: Hishta'ash'u - they became blind. Sho'u - they blinded others from seeing properly.
Malbim: They will turn repeatedly, like one who does not believe what he sees.
How did they become drunk, if not from wine?
Rashi: "Ki Nasach Aleichem Hashem" (10).
Radak: This refers to the false Nevi'im.
Malbim: They will ask - how did Bnei Ashur become drunk without wine?!
Here it says that that their inebriety was not from wine. Above (28:7), it says "Ta'u Min ha'Shechar"!
Radak: This refers to the false Nevi'im. It does not say that they do not become drunk [from wine]. Rather, even when they do not drink, they are drunk, for they are not wise and do not understand, like a drunkard.
Why does it say "Na'u v'Lo Shechar"?
Radak: The matter is repeated in different words. Na'u is like Shachru; a drunkard moves his body here and there, until he falls.
Malbim: They will ask - how did Bnei Ashur stagger like a drunkard in his vomit?! They did not drink wine! Who confounded them with panic and commotion - they became drunk and sleep forever!