The Lord hath poured out upon you the spirit of deep sleep. "Sleep," in Scripture, is sometimes "rest," "repose from trouble" ("So he giveth his beloved sleep," Psalms 128:2). But here it is "spiritual deadness and impassiveness"—an inability to appreciate, or even to understand, spiritual warnings.
The Jews of Isaiah's time were sunk in a spiritual lethargy, from which he vainly endeavored to arouse them. This spiritual lethargy is here said to have been "poured out upon them by Jehovah;" but we are not to suppose that there was anything exceptional in their treatment—"because they did not like to retain God in their knowledge, God gave them over to a reprobate mind" (Romans 1:28), as he does men generally.
Hath closed your eyes. The prophets. As the text stands, the proper translation would be, "For the Lord hath poured out upon you the spirit of deep sleep, and hath closed your eyes (the prophets), and your heads (the seers) hath he covered."
But it is reasonably conjectured that the expressions, "the prophets," "the seers," are glosses, which have crept from the margin into the text (Eichhorn, Koppe, Cheyne). If so, they are probably mistaken glosses, the allusion being, not to particular classes, but to the actual "heads" and "eyes" of individual Hebrews, which were "closed" and "covered" by the judicial action of the Almighty.
In the East a covering is often drawn over the head during sleep.