"Behold! The day is coming!" You may need to make explicit which day is coming. Alternate translation: "Behold! The day when I will punish you is coming!" (See: [[rc://en/ta/man/translate/figs-explicit]])
Possible meanings are 1) "The people of Israel have grown very proud" or "The people of Israel have become very violent and very proud." (See: [[rc://en/ta/man/translate/figs-metaphor]])