en_tn/isa/33/16.md

this is the man who will dwell on the heights, his stronghold will be the fortress among the cliffs

This speaks of the man being safe as if he lived in a home on a high hill. These two phrase are parallel and the second phrase describes the place where the man lives. Alternate translation: "he will be safe, like a man who home is built on a high hill, in a rocky place that is easy to defend" (See: rc://en/ta/man/jit/figs-metaphor and rc://en/ta/man/jit/figs-parallelism)

the heights

This refers to a high hill or mountainside. Alternate translation: "the high hill" or "the mountainside" (See: rc://en/ta/man/jit/figs-metonymy)

the fortress among the cliffs

This speaks of rocky areas that are easy to defend as if they were actually fortresses. Alternate translation: "the large piles of rocks" (See: rc://en/ta/man/jit/figs-metaphor)

will be in steady supply

"will always be available"