Hebrews 11:38

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

Revelation 6:15

and the kings of the earth, and the grandees, and the rich men, and the chief captains, and the mighty men, and every slave, and every free man, hid themselves in the caverns 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
distressed, (of whom the world was not worthy) wandering in deserts, and mountains, and dens, and caves of the earth.
Revelation 6:15
and the kings of the earth, and the grandees, and the rich men, and the chief captains, and the mighty men, and every slave, and every free man, hid themselves in the caverns and in the rocks of the mountains;