Adam Clarke on Jeremiah 51:25

O destroying mountain - An epithet which he applies to the Babylonish government; it is like a burning mountain, which, by vomiting continual streams of burning lava inundates and destroys all towns, villages fields, etc., in its vicinity.

And roll thee down from the rocks - I will tumble thee from the rocky base on which thou restest. The combustible matter in thy bowels being exhausted, thou shalt appear as an extinguished crater; and the stony mutter which thou castest out shall not be of sufficient substance to make a foundation stone for solidity, or a corner stone for beauty, Jer 51:26. Under this beautiful and most expressive metaphor, the prophet shows the nature of the Babylonish government; setting the nations on fire, deluging and destroying them by its troops, till at last, exhausted, it tumbles down, is extinguished, and leaves nothing as a basis to erect a new form of government on; but is altogether useless, like the cooled lava, which is, properly speaking, fit for no human purpose.