Hebrews 11:38

(of whom the world was not worthy,) wandering in deserts, and in mountains, and in caverns, and in dens of the earth.

Revelation 6:15

and the kings of the earth, and the great men, and the officers, and the rich men, and the mighty men, and every bondman, and every freeman, hid themselves in the caves, and in the rocks of the mountains,

Treasury of Scripture Knowledge

Summary

And the hand of Midian prevailed against Israel: and because of the Midianites the children of Israel made them the dens which are in the mountains, and caves, and strong holds.

Bible References

Dens

Hebrews 11:38
(of whom the world was not worthy,) wandering in deserts, and in mountains, and in caverns, and in dens of the earth.
Revelation 6:15
and the kings of the earth, and the great men, and the officers, and the rich men, and the mighty men, and every bondman, and every freeman, hid themselves in the caves, and in the rocks of the mountains,