'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.

In plain words: In deep, dreamless sleep a person says nothing. Still, the power to speak is not destroyed. There is simply no one else there to speak to.