Śaṅkaraon Brahma Sūtra 3.2.19

Since no substance comparable to the water is apprehended in the case of Brahman, a parallelism between Brahman and the reflected images of the sun cannot be established. In the case of the sun and other material luminous bodies, there exists a separate material substance occupying a different place, viz. water ; hence the light of the sun, &c., may be reflected. The Self, on the other hand, is not a material thing, and, as it is present everywhere and all is identical with it, there are no limiting adjuncts different from it and occupying a different place.—Therefore the instances are not parallel. The next Sutra disposes of this objection.