Adam Clarke on Isaiah 29:17

And Lebanon shall be turned into a fruitful field "Ere Lebanon become like Carmel" - A mashal, or proverbial saying, expressing any great revolution of things; and, when respecting two subjects, an entire reciprocal change: explained here by some interpreters, I think with great probability, as having its principal view beyond the revolutions then near at hand, to the rejection of the Jews, and the calling of the Gentiles. The first were the vineyard of God, כרם אל kerem El, (if the prophet, who loves an allusion to words of like sounds, may be supposed to have intended one here), cultivated and watered by him in vain, to be given up, and to become a wilderness: compare Isa 5:1-7. The last had been hitherto barren; but were, by the grace of God, to be rendered fruitful. See Mat 21:43; Rom 11:30, Rom 11:31. Carmel stands here opposed to Lebanon, and therefore is to be taken as a proper name.