Charles Ellicott Commentary 2 Kings 23:12

"And the altars that were on the roof of the upper chamber of Ahaz, which the kings of Judah had made, and the altars which Manasseh had made in the two courts of the house of Jehovah, did the king break down, and beat [them] down from thence, and cast the dust of them into the brook Kidron." — 2 Kings 23:12 (ASV)

And the altars that were on the top (roof) of the upper chamber of Ahaz. —The roof of an upper chamber in one of the Temple courts, perhaps built over one of the gateways , appears to be meant. The altars were for star-worship, which was especially practiced on housetops. (Jeremiah 32:29; Zephaniah 1:5.)

Brake them down from thence. —The Targum has removed from thence; the Septuagint pulled them down from thence (κατέσπασεν). The Hebrew probably means ran from thence, marking the haste with which the work was done. The clause thus adds a vivid touch to the narrative. It is hardly necessary to alter the points with Kimchi and Thenius, so as to read, he caused to run from thence; i.e., hurried them away.

Cast the dust of them. —Over the wall of the Temple enclosure, into the ravine beneath.