Jeremiah 21:13 - Matthew Poole's English Annotations on the Holy Bible

Inhabitant of the valley; the inhabitants of the city of Jerusalem are those here intended, Psalms 125:2. The mountains were round about Jerusalem, yea, Jerusalem itself was builded in part upon the rocky mountain of Zion; but a great part was in the valley, and the higher mountains about Mount Zion made that mountain itself, in comparison with them, as a valley. And rock of the plain; though also a rock of the plain, that is, near to the plain. Which situation of this place made the Jews think it to be impregnable, and to mock at dangers, or threats of enemies, saying, Who shall, that is, Who can or who will, dare to come against us? or, Who will be able to enter into our city? Saith the Lord, I am against you; I will come down against you, and I, by such as I shall employ, will enter into your habitations. No natural position or situation of places, no artificial fortifications, are sufficient against an almighty God.