The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c8.s4.t2.2

c8.s4.t2.2

¹ That the soul is as large as the body has been refuted in the examination of the doctrine of the Jainas (p. 651, 2). Therefore it is only possible to regard it as either very large (*i. e.* infinite, *vibhu*) or as minute (*aṇu*). The infinitely large cannot move (p. 651, 1), and we must assume of the soul that it moves because a passing (out of the body), a going (to the moon) and a return (to a new incarnation) are ascribed to it by the Scriptures (p. 650, 9). And even if the passing, so far as we regard it as a cessation of lordship over the body, could possibly be reconciled with immovability (p. 651, 5) a going and return could not; but they must certainly be recognized as motion (p. 651, 7) and we are thus compelled to regard this passing as a real going away (p. 651, 9). Since the soul, being mobile, cannot therefore be infinitely large, nor yet, as shown, of middle size, we must assume (p. 651, 8) that it is minute (*aṇu*).