BṚHADĀRAṆYAKA UPANISHAD · 4.3.26

यद् वै तन् न वदति वदन् वै तन् न वदति ।
न हि वक्तुर् वक्तेर् विपरिलोपो विद्यते ऽविनाशित्वात् ।
न तु तद् द्वितीयम् अस्ति ततो ऽन्यद् विभक्तं यद् वदेत् ॥

yad vai tan na vadati vadan vai tan na vadati ।
na hi vaktur vakter viparilopo vidyate ’vināśitvāt ।
na tu tad dvitīyam asti tato ’nyad vibhaktaṃ yad vadet ॥

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

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