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The light which shines above heaven, above all the worlds, above everything, that is the same light which is within man. We can perceive it as the warmth in the body. And of it we have this audible proof: when we thus hear, by covering the ears, what is like the rumbling of a carriage, or the bellowing of an ox, or the sound of a blazing fire. One should worship as Brahman that inner light which is seen and heard. He who knows it becomes distinct.
— Chandogya Upanishad XIII.8