Then Rezin king of Syria and Pekah the son of Remaliah, king of Israel, came up to wage war on Jerusalem, and they besieged Ahaz but could not conquer him.
Here is, 1. The attempt of his confederate neighbours, the kings of Syria and Israel, upon him. They thought to make themselves masters of Jerusalem, and to set a king of their own in it, Isa 7:6. In this they fell short, but the king of Syria recovered Elath, a considerable port upon the Red Sea, which Amaziah had taken from the Syrians, Kg2 14:22.
Commenting on 2 Kings 16:5-9
At that time Rezin king of Syria recovered Elath to Syria,.... A port on the Red sea, that formerly belonged to Edom, taken from them by David, retaken by them when they revolted in Joram's time, and perhaps taken by Amaziah again, since his son Azariah rebuilt it, and restored it to Judah, Kg2 14:22 and it seems by this that it had been in...
Then Rezin king of Syria and Pekah son of Remaliah king of Israel came up to Jerusalem--Notwithstanding their great efforts and military preparations, they failed to take it and, being disappointed, raised the siege and returned home (compare Isa 7:1).