Mundaka Upanishad by Swami Nikhilananda

 9 There the stainless and indivisible Brahman shines in the highest, golden sheath. It is pure; It is the Light of lights; It is That which they know who know the Self.

10 The sun does not shine there, nor the moon and the stars, nor these lightnings, not to speak of this fire. When He shines, everything shines after Him; by His light everything is lighted.