פירוש על אסתר 4:1

Mordechai was apprized. The Master of Dreams told him¹He was told by means of a dream and not by רוח הקדש [The Holy Spirit], a higher form of prophecy, because “Shushan was in confusion,” and רוח הקדש [The Holy Spirit] dwells only in the midst of joy. Alternatively, Eliyahu the prophet told him. that the celestial beings had consented to this [decree], because they had prostrated themselves to the idol in the days of Nevuchadnetzar, and because they had enjoyed Achashveirosh’s feast.²See Esther Rabbah 7:13 and Maseches Megillah 12a.