John Gill, on Jer 8:13

Why do we sit still?.... In the country, where were barrenness and want of provisions; in the villages and unwalled towns, where they were exposed to the spoils and ravages of the enemy. These words, with what follow, are the words of the prophet, in the language of the Israelites, as Kimchi observes. Assemble yourselves; this is the gathering together, in order to be consumed, before threatened, which they themselves were made to do: and let us enter into the defenced cities; such as Jerusalem, where they thought they should be safe from their enemies: and let us be silent there; either promising themselves rest, quietness, and security; or suggesting that it would be right in them to say nothing by way of complaint; having no reason to murmur at their afflictions, since they were no other than what their own sins had brought upon them: for the Lord our God hath put us to silence; stopped their mouths that they could not complain, being convicted in their consciences of their sins; and brought them into a state of destruction and death, which makes silent: and given us water of gall to drink; afflictions bitter and deadly. The Targum is, "and hath made us drink the cup of an evil curse, as the heads of serpents;'' a poisonous and deadly potion: because we have sinned against the Lord; which they were obliged to own; though it does not appear that they had true repentance for their sins, or amended their ways; sometimes confession of sin is made without either of these.