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 Judges 5:5; 1-Kings 19:11; Psalm 65:6; Psalm 114:4; Psalm 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 without their suspecting any such thing; compare Psalm 35:8. "Let destruction come upon him at unawares," or, as it is in the Hebrew and in the margin, "which he knoweth not of." Tindal renders this, "He translatethe the mountaynes or ever they be aware."
Which overturneth them in his anger - As if he were enraged. There could scarcely be any more terrific exhibition of the wrath of God than the sudden and tremendous violence of an earthquake.

Removeth the mountains, and they know not - This seems to refer to earthquakes. By those strong convulsions, mountains, valleys, hills, even whole islands, are removed in an instant; and to this latter circumstance the words, they know not, most probably refer. The work is done in the twinkling of an eye; no warning is given; the mountain, that seemed to be as firm as the earth on which it rested, was in the same moment both visible and invisible; so suddenly was it swallowed up.

Which removeth the mountains,.... 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 (y) furnishes us with instances of mountains being removed from one place to another; and Scheuchzer (z) 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, one half to the north and the other to the south, Zac 14:4; and Josephus (a) gives a relation much like it, as in fact; besides, Job may have respect to what had been done in his times, or before them, and particularly at the universal deluge, which covered the tops of the highest mountains and hills, and very probably washed away some from their places: or else it may be understood proverbially, of the Lord's doing things marvellous and surprising, and which are impossible and impracticable with men; see Matthew 17:20; or rather figuratively, of kingdoms and mighty kings, as the Targum, comparable to mountains for their height and strength, who yet are removed by God at his pleasure; see Zac 4:7,
and they know not; when they are removed, and how it is done; it is imperceptible; either the mountains are not sensible of it, or the inhabitants of the mountains, as Bar Tzemach; or men, the common sort of men, the multitude, as Gersom: R. Saadiah Gaon interprets it of removing the men of the mountains, and they know it not:
which overturneth them in his anger; for the sins or men, which was the case of the old world: Mr. Broughton renders it, "that men cannot mark how he hath removed them out of their place in his anger".
(y) Plin. Nat. Hist. l. 2. c. 83. Wernerus, Palmerius, Theophanes "a aurus", in Bolduc. in loc. (z) Physic. Sacr. vol. 4. p. 673. (a) Antiqu. l. 9. c. 10. sect. 4.

and they know not--Hebrew for "suddenly, unexpectedly, before they are aware of it" (Psalm 35:8); "at unawares"; Hebrew, which "he knoweth not of" (Joel 2:14; Proverbs 5:6).

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 Ezekiel 20:26; Ecclesiastes 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, and effects its purpose suddenly. He causes the earth to start up from its place (comp. Isaiah 13:13) which it occupies in space (Job 26:7); and by being thus set in motion by Him, its pillars tremble, i.e., its internal foundations (Psalm 104:5), which are removed from human perception (Job 38:6). It is not the highest mountains, which are rather called the pillars, as it were the supports, of heaven (Job 26:11), that are meant. By the same almighty will He disposes of the sun and stars. The sun is here called חרס (as in Judges 14:18 חרסה with unaccented ah, and as Isaiah 19:18 ‛Ir ha-Heres is a play upon החרס עיר, Ἡλιούπολις), perhaps from the same root as חרוּץ, one of the poetical names of gold. At His command the sun rises not, and He seals up the stars, i.e., conceals them behind thick clouds, so that the day becomes dark, and the night is not made bright. One may with Schultens think of the Flood, or with Warburton of the Egyptian darkness, and the standing still of the sun at the word of Joshua; but these are only single historical instances of a fact here affirmed as a universal experience of the divine power.

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.