They stoop, they bow down together; they could not deliver the burden, but themselves are gone into captivity. They could not deliver the burden "They could not deliver their own charge" - That is, their worshippers, who ought to have been borne by them. See the two next verses. The Chaldee and Syriac Versions render it in effect to the same purpose, those that bear them, meaning their worshippers; but how they can render משא massa in an active sense, I do not understand.
For לא lo, not, ולא velo, and they could not, is the reading of twenty-four of Kennicott's, sixteen of De Rossi's, and two of my own MSS. The added ו vau gives more elegance to the passage.
But themselves "Even they themselves" - For ונפשם venaphsham, an ancient MS. has כי נפשם ki naphsham, with more force.