ज्योतिषामपि तज्ज्योतिस्तमसः परमुच्यते | ज्ञानं ज्ञेयं ज्ञानगम्यं हृदि सर्वस्य विष्ठितम् || १८ ||
jyotiṣām api taj jyotis tamasaḥ param ucyate jñānaṁ jñeyaṁ jñāna-gamyaṁ hṛdi sarvasya viṣṭhitam
jyotiṣām—of all luminaries; api—also; tat—that; jyotiḥ—source of light; tamasaḥ—of darkness; param—beyond; ucyate—is said; jñānam—knowledge; jñeyam—the knowable; jñāna-gamyam—reached by knowledge; hṛdi—in the heart; sarvasya—of all; viṣṭhitam—seated.
“That is the Light of all lights, said to be beyond darkness; It is knowledge, the knowable, and that which is attained through knowledge — seated in the heart of all.”
This verse is one of the most luminous in the Gita. Brahman is the 'light of all lights' — meaning it is the consciousness that illumines the sun, the moon, fire, and even the intellect. All other forms of light are secondary; they illuminate objects, but they cannot illuminate themselves. Only Brahman — pure consciousness — illumines all, including itself, being self-luminous. And this self-luminous reality dwells in the heart (hrdi) of every being, accessible from within.
The teaching that this Reality dwells in your own heart ('hrdi sarvasya vishthitam') is the most practically significant statement in this section. You need not go anywhere, achieve anything, or become different. The Light of all lights is already present as the witnessing awareness in your own heart. The practice is simply the turning of attention inward, from objects to the awareness that knows all objects.