And upon all the high mountains - Judea abounded in lofty mountains, which added much to the grandeur of its natural scenery. Lowth supposes that by mountains and hills are meant here, ‘kingdoms, republics, states, cities;’ but there are probably no parallel places where they have this meaning. The meaning is probably this: high mountains and hills would not only be objects of beauty or grandeur, but also places of defense, and protection. In the caverns and fastnesses of such hills, it would be easy for the people to find refuge when the land was invaded. The meaning of the prophet then is, that the day of God’s vengeance should be upon the places of refuge and strength; the strongly fortified places, or places of sure retreat in cases of invasion; compare the notes at Isaiah 2:19.
Hills that are lifted up - That is, high, elevated hills.