Adam Clarke on Isaiah 51:13

Of the oppressor, as if he, etc. - "The כ caph in כאשר keasher seems clearly to have changed its situation from the end of the preceding word to the beginning of this; or rather, to have been omitted by mistake there, because it was here. That it was there the Septuagint show by rendering המציקך hammetsikech θλιβοντος σε, of him, that oppressed thee. And so they render this word in both its places in this verse. The Vulgate also has the pronoun in the first instance; furoris ejus qui te tribulabat." Dr. Jubb. The correction seems well founded; I have not conformed the translation to it, because it makes little difference in the sense.