MUṆḌAKA UPANISHAD · 2.2.9

हिरण्मये परे कोशे विरजं ब्रह्म निष्कलम् ।
तच्छुभ्रं ज्योतिषां ज्योतिस्तद्यदात्मविदो विदुः ॥ ९॥

hiraṇmaye pare kośe virajaṃ brahma niṣkalam ।
tacchubhraṃ jyotiṣāṃ jyotistadyadātmavido viduḥ ॥ 9॥

In a supreme golden sheath the Brahman lies, stainless, without parts. A Splendour is That, It is the Light of Lights, It is That which the self-knowers know.