What does Ezekiel 21:28 mean?

And you, son of man, give this message from the Lord God about the Ammonites and their insults: Say, ‘A sword is drawn for slaughter, polished to destroy, flashing like lightning.’ Ezekiel 21:28 - Modern Text Bible

(God tells Ezekiel to warn the Ammonites that judgment is coming for them too, not just Israel.)