God summons three witnesses to hear His sentence.
(1) the Gentiles.
(2) all mankind, Jews and Gentiles.
(3) nature (see Jeremiah 6:19).
What is among them - Rather, “what happens” in them; i. e., “Know what great things I will do to them.”
Related Commentaries of Jeremiah 6:18
Jeremiah 6:18
18 Therefore hear, ye nations, and know, O congregation, what is among them.