Job 9:5

“Which removeth the mountains, etc.] This and what follow are instances of the power of God, and are full proofs of his being mighty in strength; and may be understood, either literally, not only of what God is able to do if he will, but of what he has done; and history f371 furnishes us with instances of mountains being removed from one place to another; and Scheuchzer f372 makes mention of a village in Helvetia, called Plurium, which, in 1618, was covered with the sudden fall of a mountain, and swallowed up in the earth, with 1800 inhabitants, and not the least trace of it to be seen any more; and in the sacred Scriptures is a prediction of the mount of Olives being removed from its place,…”

“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).”

“Which removeth the mountains - In order to show how vain it was to contend with God, Job refers to some exhibitions of his power and greatness. The “removal of the mountains” here denotes the changes which occur in earthquakes and other violent convulsions of nature. This illustration of the power of God is often referred to in the Scriptures; compare Jdg 5:5; 1 Kings 19:11; Psalms 65:6; Psalms 114:4; Psalms 144:5; Isaiah 40:12; Jeremiah 4:24. And they know not - This is evidently a Hebraism, meaning suddenly, or unexpectedly. He does it, as it were, before they are aware of it. A similar expression occurs in the Koran, “God overturns them, and they do not know it;” that is, he does it…”

“Who - He proceeds to give evidence of the Divine power and wisdom. Removeth - Suddenly and unexpectedly. They - The mountains, to which he ascribes sense and knowledge figuratively. In anger - In token of his displeasure with the men that live upon them. Job 9:6”

“9:5-6 When God moves the mountains and when the foundations of the earth tremble, it is a sign of his presence as lawgiver (Exod 19:18), judge (Jer 4:24), or rescuer (Ps 18:7; Isa 13:13; 29:6).”

“removeth: Job 28:9; Psa 46:2, Psa 68:8, Psa 114:6; Isa 40:12; Hab 3:6, Hab 3:10; Zac 4:7; Mat 21:21; Co1 13:2; Rev 6:14, Rev 11:13 which overturneth: Num 1:5, Num 1:6; Zac 14:4, Zac 14:5; Mat 27:51; Luk 21:11; Rev 16:18-20 Job 9:6”

“5 Who removeth mountains without their knowing, That He hath overturned them in His wrath; 6 Who causeth the earth to shake out of its place, And its pillars to tremble; 7 Who commandeth the sun, and it riseth not, And sealeth up the stars. ידעוּ ולא ( Job 9:5) may also be translated: without one's perceiving it or knowing why; but it is more natural to take the mountains as the subject. אשׁר, quod, that (not "as," Ewald, 333, a), after ידע, as Eze 20:26; Ecc 8:12. Even the lofty mountains are quite unconscious of the change which He effects on them in a moment. Before they are aware that it is being done, it is over, as the praet. implies; the destructive power of His anger is irresistible,…”