The people shall labor in the very fire - All these superb buildings shall be burnt down. See the parallel passage, Jeremiah 51:58; (note), and the note there.
Shall weary themselves for very vanity? - For the gratification of the wishes of ambition, and in buildings which shall be brought to naught.
Behold, is it not of the Lord of hosts that (the) people (nations) shall labor - o
In (for) the very fire - literally, to suffice the fire? By God‘s appointment, the end of all their labor is for the fire, what may suffice it to consume. This is the whole result of their labor; and so it is as if they had toiled for this; they built ceiled palaces and gorgeous buildings, only for the fire to consume them.
And the peoples shall weary themselves for very vanity - They wearied themselves, and what was their reward? What had they to suffice and fill them? “Emptiness.” This is “from the Lord of hosts,” whom all the armies of heaven obey and all creatures stand at His command against the ungodly, and in whose Hand are all the hosts of earth, and so the oppressor‘s also, to turn as He wills.
Near upon the first stage of the fulfillment, Jeremiah reinforces the words with the name of Babylon; Jeremiah 51:58: “Thus saith the Lord of hosts! The broad walls of Babylon, shall be utterly destroyed, and her high gates shall be burned with fire; and the people shall labor in vain (for vanity), and the folk in (for) the fire, and they shall be weary.”