। ॥ ६०३ ॥
In plain words
The intellect and everything it could show you dissolve, and this one is left alone: in deep sleep it sees nothing, hears nothing, knows nothing at all. Of itself, with no help, it stands as the witness of that sleeping darkness — and stays there at ease, undivided.
Close to the Sanskrit
Because of the dissolution of the knowables beginning with the intellect, this one alone, in deep sleep, does not see, does not hear, does not know anything; having become of himself alone the witness of the darkness belonging to deep sleep, he remains here, at ease and without any mental division.