大方廣佛華嚴經隨疏演義鈔 21.46

21.46

疏「夢是神遊」，《漢武故事》說：昔漢武帝欲試善元夢者，乃詐為夢云：「朕夢見殿上兩瓦化為鴛鴦飛空而去。是何徵也？」元夢者曰：「宮中必有相殺暴死之者。」帝曰：「戲之耳。」言未畢，監司奏云：「宮人相殺。」帝曰：「朕實不夢而有徵者，何耶？」對曰：「夢是神遊。陛下欲言，即夢也。」

Regarding the commentary's statement that "a dream is the roaming of the spirit": the Hanwu gushi relates: Formerly, Emperor Wu of Han wished to test someone skilled at interpreting dreams, and falsely claimed to have had a dream, saying: "We dreamed that two tiles upon the palace hall turned into mandarin ducks and flew away into the air. What does this portend?" The dream interpreter said: "There must be someone in the palace who will be murdered and die violently." The Emperor said: "I was only joking." Before he had finished speaking, the supervising officer memorialised: "Palace attendants are killing one another." The Emperor said: "We truly did not dream it, yet there was a sign—why is this?" He replied: "A dream is the roaming of the spirit. When Your Majesty intended to speak of it, that was itself a dream."