Bhagavad Gita 13.18
It is the light of lights, beyond the reach of darkness; the wisdom, the only thing worth knowing or that wisdom can teach; the presence in the hearts of all.
ज्योतिषामपि तज्ज्योतिस्तमसः परमुच्यते।ज्ञानं ज्ञेयं ज्ञानगम्यं हृदि सर्वस्य विष्ठितम्॥jyotiṣāmapi tajjyotistamasaḥ paramucyate|jñānaṃ jñeyaṃ jñānagamyaṃ hṛdi sarvasya viṣṭhitam||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).