John Gill Commentary Jeremiah 38:18

"But if thou wilt not go forth to the king of Babylon`s princes, then shall this city be given into the hand of the Chaldeans, and they shall burn it with fire, and thou shalt not escape out of their hand." — Jeremiah 38:18 (ASV)

But if you will not go forth to the king of Babylon's
princes
And surrender to them: then shall this city be given into the hands of the Chaldeans ;
if not willingly delivered up by the king of Judah, it shall be forcibly taken by the king of Babylon's army, through the permission of God; with respect to whom it is said to be given to them, even by him who has the disposing of cities and kingdoms: and they shall burn it with fire ;
as it had been often foretold it should, and as it accordingly was, (Jeremiah 39:8) ;

and you shall not escape out of their hand ;
though he might hope he should, and would attempt to do it, yet should be taken; and though he should not be slain, yet should never regain his liberty, or get out of their hands, when once in them; see (Jeremiah 52:7–9Jeremiah 52:11) .