Job 9:5

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 - 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.

9:5 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.