The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
25. And as in the case of (physical) light and the like, there is non-distinction (of the two Selfs), the light (i.e. the intelligent Self) (being divided) by its activity; according to the repeated declarations of scripture.
As light, ether, the sun and so on appear differentiated as it were through their objects such as fingers, vessels, water and so on which constitute limiting adjuncts 2, while in reality they preserve their essential non-differentiatedness; so the distinction of different Selfs is due to limiting adjuncts only, while the unity of all Selfs is natural and original. For on the doctrine of the non-difference of the individual soul and the highest Self the Vedânta-texts insist again and again. 3
172:2 Light is differentiated as it were by the various objects on which it shines; the all-pervading ether is divided into parts as it were by hollow bodies; the sun is multiplied as it were by its reflections in the water.
172:3 It certainly looks here as if the Bhâshyakâra did not know what to do with the words of the Sûtra. The 'karmani,' which is p. 173 as good as passed over by him, is explained by Go. Ân. as 'dhyânâdikarmany upâdhau.' Ân. Gi. says, 'âtmâprakâsasabditoऽgñânatatkârye karmany upâdhau saviseshas' &c.