Adam Clarke's Commentary on the Bible

Verse 6 (Job 9:6)

The pillars thereof tremble - This also refers to an earthquake, and to that tremulous motion which sometimes gives warning of the approaching catastrophe, and from which this violent convulsion of nature has received its name. Earthquakes, in Scripture language, signify also violent commotions and disturbances in states; mountains often signify rulers; sun, empires; stars, petty states. But it is most likely that the expressions here are to be understood literally.

- Adam Clarke's Commentary on the Bible