ישעיהו כא:יא קבלה: זוהר

Therefore, it is written, "The burden of Dumah. One calls to me out of Seir, Watchman, what of the night? Watchman, what of the night?" (Isaiah 21:11), for the dominion of Esau, who is called 'Se'ir', is during the night. Therefore the angel weakened when morning came, and then "he said, Let me go, for the day breaks."