Hebrews 11:38

(Of whom the world was not worthy:) they wandered in deserts, and in mountains, and in dens and caves of the earth.

Of whom the world was not worthy - So far from their being unworthy of living in the world, as their exile in desert, etc., might imply. The world, in shutting them out, shut out from itself a source of blessing; such as Joseph proved to Potiphar and Jacob to Laban (Genesis 30:27; Genesis 39:5). In condemning them, the world condemned itself.

Caves, [ opais (G3692)] - 'chinks.' Palestine, from its hilly character, abounds in fissures and caves, affording shelter to the persecuted, as the 50 men hid by Obadiah and Elijah (1 Kings 18:4; 1 Kings 18:13; 1 Kings 19:8; 1 Kings 19:13); Mattathias and his sons ( 1Ma 2:28-29 ); Judas Maccabeus ( 2Ma 5:27 ).