en_tn_condensed/isa/28/04.md

that is on the head of the rich valley

The city of Samaria, the capital of Israel, sits above a fertile valley. (See: rc://en/ta/man/translate/figs-metaphor)

will be as the first ripe fig ... gulps it down

This speaks of the enemy soldiers seeing the beauty of Samaria and quickly plundering it as if they were a person who sees the first fig of the season and quickly eats it. (See: rc://en/ta/man/translate/figs-simile)