Woe to thee that spoilest. The "spoiler" is here, evidently, Assyria—the world-power of this entire group of prophecies (see especially Isaiah 30:31; Isaiah 31:8), and the greatest "spoiler" of Isaiah's time.
Thou wast not spoiled; i.e. "that hast not yet been spoiled thyself." A covert threat is conveyed in the words. And dealest treacherously; rather, usest violence (compare the comment on Isaiah 21:2).
When thou shalt cease to spoil, etc. Conquering nations cannot with safety pause on their career. Their aggressions have roused so many enmities that, let them cease to attack, and at once they are attacked in their turn.
Every man's baud is against the spoiler whose hand has been against every man.