And they know not— And they are not broken to pieces: an instance of the power of the Almighty, who can remove whole mountains as easily as the least pebble. See Heath, and Judges 8:16. Schultens and Houbigant render it, on a sudden, unawares. See Psalms 35:8.
Related Commentaries of Job 9:5
Job 9:5
5 Which removeth the mountains, and they know not: which overturneth them in his anger.