Adam Clarke on Isaiah 51:11

They shall obtain gladness and joy, and sorrow and mourning shall flee away - Nineteen MSS. and the two oldest editions have ישגו yasigu; and forty-six MSS. of Kennicott's and ten of De Rossi's, and the same two editions, and agreeably to them the Chaldee and Syriac, have ונסו venasu; and so both words are expressed, Isa 35:10, of which place this is a repetition. And from comparing both together it appears that the ו vau in this place is become by mistake in the present text final, nun of the preceding word.