'On this there are these verses: 'After having subdued by sleep all that belongs to the body, he, not asleep himself, looks down upon the sleeping (senses). Having assumed light, he goes again to his place, the golden person, the lonely bird.

In plain words: An old verse says that in sleep the Self quiets the body and senses but does not sleep itself. It watches over them, and then returns to its place, shining like a golden person or a lonely bird.