The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut [1890] at sacred-texts.com
28. For thus it is in the (individual) Self also, and various (creations exist in gods 1, &c.).
Nor is there any reason to find fault with the doctrine that there can be a manifold creation in the one Self, without destroying its character. For Scripture teaches us that there exists a multiform creation in the one Self
of a dreaming person, 'There are no chariots in that state, no horses, no roads, but he himself creates chariots, horses, and roads' (Bri. Up. IV, 3, 10). In ordinary life too multiform creations, elephants, horses, and the like are seen to exist in gods, &c., and magicians without interfering with the unity of their being. Thus a multiform creation may exist in Brahman also, one as it is, without divesting it of its character of unity.
352:1 This is the way in which Sankara divides the Sûtra; Ân. Gi. remarks to 'loke#po, &c.: âtmani keti vyâkhyâya vikitrâs ka hîti vyâkashte.'