John Gill Commentary Isaiah 13:7

"Therefore shall all hands be feeble, and every heart of man shall melt:" — Isaiah 13:7 (ASV)

Therefore shall all hands be faint
Or hang down; that is, the hands of all the Babylonians, the city being taken suddenly and at once, so that they should not be able to lift them up to lay hold on a weapon, and defend themselves:

and every man's heart shall melt ;
like wax before the fire; be dispirited, and lose all their valour and courage, have neither power nor heart to resist their enemies, and attempt to save themselves.