Adam Clarke on Isaiah 30:19

For the people shall dwell in Zion "When a holy people shall dwell in Sion" - Λαος ἁγιος, Septuagint; עם קדוש am kadosh. The word קדוש dro kadosh, lost out of the text, but happily supplied by the Septuagint, clears up the sense, otherwise extremely obscure. When the rest of the cities of the land were taken by the king of Assyria, Zion was preserved, and all that were in it.

Thou shalt weep no more "Thou shalt implore him with weeping" - The negative particle לא lo is not acknowledged by the Septuagint. It may perhaps have been written by mistake for לו lo, to him, of which there are many examples.