Adam Clarke Bible Commentary

And the covert for the Sabbath - There are a great number of conjectures concerning this covert, or, as it is in the Hebrew, the מוסך musach, of the Sabbath. As the word, and others derived from the same root, signify covering or booths, it is very likely that this means either a sort of canopy which was erected on the Sabbath days for the accommodation of the people who came to worship, and which Ahaz took away to discourage them from that worship; or a canopy under which the king and his family reposed themselves, and which he transported to some other place to accommodate the king of Assyria when he visited him. Jarchi supposes that it was a sort of covert way that the kings of Judah had to the temple, and Ahaz had it removed lest the king of Assyria, going by that way, and seeing the sacred vessels, should covet them. If that way had been open, he might have gone by it into the temple, and have seen the sacred vessels, and so have asked them from a man who was in no condition to refuse them, however unwilling he might be to give them up. The removing of this, whatever it was, whether throne or canopy, or covered way, cut off the communication between the king's house and the temple; and the king of Assyria would not attempt to go into that sacred place by that other passage to which the priests alone had access.