John Gill Commentary Ezekiel 24:12

"She hath wearied [herself] with toil; yet her great rust goeth not forth out of her; her rust [goeth not forth] by fire." — Ezekiel 24:12 (ASV)

She has wearied herself with lies With serving idols, which were lying vanities; by trusting to the alliances of neighboring nations, which deceived her; or by committing sin, in which there was no satisfaction; or it may be understood of wearying of God with their sins, and particularly with her lying promises of repentance and reformation.

and her great scum did not go forth out of her Notwithstanding her promises; or notwithstanding the admonitions given, and the chastisements inflicted on her, yet she continued hardened in her sins, impenitent and unreformed:

her scum shall be in the fire Like a pot that boils over, its scum falls into the fire, and is consumed there; and in no other way, but by the fire of divine judgments, or the burning of the city, could the wickedness of the city be consumed.

The Targum is, "and they shall not go out of her that work iniquity; in the fire shall she be burnt, because of the multitude of her sins."