Bhagavad Gita Chapter 13, Verse 18

ज्योतिषामपि तज्ज्योतिस्तमसः परमुच्यते | ज्ञानं ज्ञेयं ज्ञानगम्यं हृदि सर्वस्य विष्ठितम् ||

jyotiṣām api taj jyotis tamasaḥ param ucyate jñānaṁ jñeyaṁ jñāna-gamyam hṛdi sarvasya viṣṭhitam

It is the light of all lights, said to be beyond darkness. It is knowledge, that which is to be known, and that which is to be attained through knowledge. It is situated in the hearts of all.

Krishna completes the description of the Supreme. 'Jyotiṣām api taj jyotis'—it is the light of all lights. The Supreme is the source of all light—physical, mental, spiritual. 'Tamasaḥ param ucyate'—it is said to be beyond darkness. The Supreme is beyond ignorance, beyond the field's limitations. 'Jñānaṁ jñeyaṁ jñāna-gamyam'—it is knowledge, that which is to be known, and that which is to be attained through knowledge. The Supreme is the source of knowledge, the object of knowledge, and the goal of knowledge. 'Hṛdi sarvasya viṣṭhitam'—it is situated in the hearts of all. The Supreme is present in everyone—not distant, not separate, but present in the heart. This verse completes the description of the Supreme as the ultimate knower—the light that illuminates all, beyond darkness, present in all hearts. When you understand this, you recognize the Supreme as the ultimate reality—the source of all, present in all, the goal of all knowledge.