Albert Barnes Commentary Jeremiah 21:13

"Behold, I am against thee, O inhabitant of the valley, [and] of the rock of the plain, saith Jehovah; you that say, Who shall come down against us? or who shall enter into our habitations?" — Jeremiah 21:13 (ASV)

Inhabitant - is feminine, the population of Jerusalem being always personified as a woman, the daughter of Zion. Omit and. Jerusalem is at once a valley and a rock (Jeremiah 17:3). The people are described as priding themselves on the impregnability of their city.