Bhāṣya
य इति स्वतःसिद्धतामाह ।एकः अद्वितीयः विभाति विशेषेण प्रकाशते स्वतः स्वयमेव न परतः शुद्धं निर्मलं चेतो मनो यस्य सः स्वतःशुद्धचेताः ; शुद्धचित्तस्य हि आत्मा स्वयमेव स्फुरतीत्यर्थः ।अत एव सत्त्वशुद्ध्यर्थं वेदेऽपि वेदानुवचनादयो विहिताः — ‘तमेतं वेदानुवचनेन ब्राह्मणा विविदिषन्ति यज्ञेन दानेन तपसानाशकेन’ इति ।घटपटादयश्च जडत्वात् प्रकाशान्तरापेक्षत्वाच्च न प्रकाशन्त इति युक्तम् ।आत्मा तु प्रकाशस्वरूपत्वात् प्रकाशान्तरानपेक्षः प्रकाशते सवितृवत् — यथा सविता स्वप्रकाशः प्रकाशान्तरं नापेक्षते अथ च प्रकाशते, तद्वदात्मापीति भावः ।एवमुत्पन्नात्मज्ञानो अद्वयो जीवन्मुक्तः स्वयं प्रकाशरूपोऽपि परमार्थतो नानाविधासु धीषु उपाधिषु नानेव भाति यः, सोऽहमात्मेति सम्बन्धः ।शरावोदकेषु उपाधिषु अवस्थितो भानुः आदित्यः प्रकाशस्वरूपोऽपि एक एव सन् नानेव भाति, तद्वदात्मापीति भावः ।
In plain words
That verse establishes the self-proven reality of the Self. The One, non-dual consciousness shines forth entirely by its own light, independent of anything else, when the mind is spotlessly pure. For one whose inner organ is cleansed, the Self spontaneously reveals itself. This is why the Vedas prescribe disciplines like sacred study, sacrifice, charity, and austerity to purify the heart, as the scripture declares: 'Seekers of Brahman desire to know this very Self through study, sacrifice, gift, and austerity.' Insentient objects like pots and cloth depend on an external light to be seen; but the Self is light itself and needs no other illumination. Like the sun, which is self-luminous and shines without needing another source, so too is the Self. Thus, the person who has awakened to the non-dual Self and is liberated while living remains pure consciousness, yet appears as many within the varied limiting conditions of the mind—just as the single sun, reflected in many bowls of water, appears as many suns while remaining one and indivisible.
Close to the Sanskrit
That declares self-establishedness. One, non-dual, shines forth, illuminates specifically, spontaneously and by itself, not from another; whose mind is pure and stainless: the meaning is that for one of pure mind, the Self shines forth by itself indeed. Hence indeed, for the purification of the mind, practices such as Vedic recitation are prescribed in the Veda also — 'This very Self do the Brahmins seek to know through Vedic recitation, sacrifice, gift, austerity, and non-wasting fasting' thus. Pots, cloths, and others, being insentient and needing another light, do not shine—this is appropriate. But the Self, being of the nature of light and not needing another light, shines like the sun—just as the sun is self-luminous, does not expect another light, and yet shines, so is the Self also, this is the purport. Thus, one who has realized the Self, non-dual, liberated while living, though of the nature of self-illumination, ultimately appears as if manifold in various intellects and limiting adjuncts: 'I am that Self' is the connection. As the sun, the luminary situated in limiting adjuncts such as water in shallow bowls, though of the nature of light and being one only, appears as if manifold, so is the Self also, this is the purport.