BṚHADĀRAṆYAKA UPANISHAD · 4.3.27

यद् वै तन् न शृणोति शृण्वन् वै तन् न शृणोति ।
न हि श्रोतुः श्रुतेर् विपरिलोपो विद्यते ऽविनाशित्वात् ।
न तु तद् द्वितीयम् अस्ति ततो ऽन्यद् विभक्तं यच् छृणुयात् ॥

yad vai tan na śṛṇoti śṛṇvan vai tan na śṛṇoti ।
na hi śrotuḥ śruter viparilopo vidyate ’vināśitvāt ।
na tu tad dvitīyam asti tato ’nyad vibhaktaṃ yac chṛṇuyāt ॥

'And when (it is said that) there (in the Sushupti) he does not hear, yet he is hearing, though he does not hear. For hearing is inseparable from the hearer, because it cannot perish. But. there is then no second, nothing else different from him that he could hear.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)