LORD, when thy hand is lifted up, they will not see: but they shall see, and be ashamed for their envy at the people; yea, the fire of thine enemies shall devour them.
Lord, (when) thy hand is lifted up - to punish the foes of God's people. They who will not see, shall be made to "see" to their cost (Isaiah 5:12).
(But) they shall see, and be ashamed for (their) envy at the (i:e., thy) people. Lowth translates, 'they shall see with confusion thy zeal for thy people.' This is confirmed by the parallel.
The fire of thine enemies shall devour them - i:e., the fire of thy vengeance, to which thine enemies are doomed (Isaiah 9:18).