Rejoice not thou: i.e. at the death of Ahaz, and because the Davidic dominion was broken by the Syro- Ephraimitic war.
Palestina. Philistia.
him. the Davidic power.
for out of the serpent's root, &c. That was how Philistia regarded Judah and Ahaz.
cocktrice. viper (see note on Isaiah 11:8), which they would find in his son Hezekiah in the immediate future (2 Kings 18:8).