He moves mountains without their knowledge and overturns them in His anger.
Bildad began with a rebuke to Job for talking so much, Job 8:2. Job makes no answer to that, though it would have been easy enough to retort it upon himself; but in what he next lays down as his principle, that God never perverts judgment, Job agrees with him: I know it is so of a truth, Job 9:2.
Commenting on Job 9:1-13
Which shaketh the earth out of her place,.... Can do it, and will do it at the last day, when it shall be utterly broken down, clean dissolved, and reel to and fro like a drunkard, and be removed as a cottage, and which John in a vision saw flee away from the presence of him that sat upon the throne, Isa 24:19; for this...
and they know not--Hebrew for "suddenly, unexpectedly, before they are aware of it" (Psa 35:8); "at unawares"; Hebrew, which "he knoweth not of" (Joe 2:14; Pro 5:6).