華嚴經探玄記 5.61

5.61

五意中幻夢者，以睡中意識行故，夢中所見能所等事，皆心幻作故也。此中覺觀等既是心法，猶是舉數以徵王也。

Fifth, in mind, illusions and dreams are because the mental consciousness operates during sleep, and the objects, subjects, and so forth seen in dreams are all created by the mind as illusions. Here, since coarse and subtle investigation (vitarka and vicāra) and so forth are mental factors, it is still adducing the mental factors to interrogate the king of mind.