Mandukya Karika, verse 4.81

Text

अजमनिद्रमस्वप्नं प्रभातं भवति स्वयम् ।
सकृद्विभातो ह्येवैष धर्म धातुस्वभावतः ॥ ८१ ॥

ajamanidramasvapnaṃ prabhātaṃ bhavati svayam |
sakṛdvibhāto hyevaiṣa dharma dhātusvabhāvataḥ || 81 ||

81. (Reality which is) free from birth, (which is) free from sleep and dream, reveals itself by itself For, this Dharma (i.e., Ātman) is from its very nature ever-luminous.

Shankara Bhashya (commentary)

The nature of that which is realisable by the wise is again described:—It (Ātman) reveals itself by itself. It does not depend for its revelation upon any external1 light, such as the sun, etc. Self-luminosity2 is its very nature. It is ever-luminous. This is the inherent characteristic of the Dharma, known as Ātman.