Albert Barnes Commentary Job 30:6

"So that they dwell in frightful valleys, In holes of the earth and of the rocks." — Job 30:6 (ASV)

To dwell in the cliffs of the valleys - The word translated here as “cliffs” (ערוץ ‘ârûts) rather denotes “horror,” or something “horrid.” The sense here is that they dwelt in “the horror of valleys;” that is, in horrid valleys.

This conveys the idea of deep and frightful glens, where wild beasts roamed, far from human settlements, and surrounded by desolate wastes.

The word translated as “valleys” (נחל nachal) properly means a brook, stream, or watercourse—what is now called a wadi. This refers to a place where winter torrents flow but which is usually dry in summer (see the notes at Job 6:15).

In caves of the earth - The marginal note, following the Hebrew, reads “holes.” The Septuagint states: “Whose houses are πρῶγλαι πετρῶν trōglai petrōn — caverns of the rocks;” that is, those who are “Troglodytes.”

Caves provided a natural dwelling for the poor and the outcast. It is well known that it was not uncommon in Egypt and the deserts of Arabia for people to occupy such caves as habitations (see Diodorus Siculus, Book 3, Chapter 14, and Strabo, Book 16).

And in the rocks - This refers to the caverns of the rocks.

Dr. Richardson found many such dwellings in the vicinity of Thebes, many of which were large, beautifully formed, and sculpted with many intricate designs. Mr. Rich also saw many similar caves not far from Mosul (see his Residence in Kurdistan, vol. 2, p. 94).