यत्रात्मनोऽकामयितृत्वबुद्धिःस्वप्नानपेक्षापि च तत्सुषुप्तम् ।इत्यात्मसद्भाव उदीर्यतेऽत्रश्रुत्यापि तस्माच्छ्रुतिरत्र मानम् ॥ ६०७ ॥
In plain words
Where the Self is known as one who desires nothing, and no dream is looked for either — that state is deep sleep. So it is śruti itself that declares, here, that the Self is really present. And that is why, on this point, śruti is the measure.
Close to the Sanskrit
Where there is the cognition of the Self's non-desirership, and also the absence of any regard for dreams — that is deep sleep. Thus, here, the real existence of the Self is declared by śruti also; therefore śruti is the means of knowledge here.