Matthew Poole and continuators on Isaiah 42:15

15. I will make wast mountains and hills , and dry up all their herbs, and I will make the rivers islands, and I will dry up the pools .

Not dry and barren ones, for these were wast already, but such as are clothed with Grass and Herbs, as the following words imply. Which is to be understood Metaphorically, of Gods destroying his most lofty and flourishing enemies, who are oft compared in Scripture unto Mountains and Hills.

I will remove all impediments out of the way: which is expressed in the Prophetical dialect, by drying up Euphrates, that the way of the Kings of the East might be prepared, Revel. 16. 12. He seems to allude to that which God did in drying up first the Red Sea, and then Iordan, to give his people passage into Canaan. And this exposition is confirmed by the following verse.