The great day of the LORD is near, it is near, and hasteth greatly, even the voice of the day of the LORD: the mighty man shall cry there bitterly.
The voice of the day of the Lord - i:e., Yahweh ushering in that day with a roar of vengeance against the guilty (Jeremiah 25:30; Amos 1:2, "The Lord will roar from Zion, and utter his voice from Jerusalem"). They who will not now heed (Zephaniah 1:12) His voice by His prophets, must heed it when uttered by the avenging foe.
The mighty man shall cry there bitterly - in hopeless despair; the might on which Jerusalem now prides itself shall then fail utterly.