Sutra 3.2.7

7. The absence of that takes place in the nāḍīs and in the Self, according to scriptural statement.

Next the state of deep dreamless sleep is enquired into. Scripture says, 'When a man is asleep, reposing and at perfect rest, so that he sees no dream, then he lies asleep in those nāḍīs' (Ch. Up. VIII, 6, 3); 'When he is in profound sleep and is conscious of nothing, there are seventy-two thousand veins called hita which from the heart spread through the pericardium. Through them he moves forth and rests in the pericardium' (Bṛ. Up. II, 1, 19). 'When a man sleeps here, he becomes united with the True' (Ch. Up. VI, 8, 1). These texts declare the veins, the pericardium, and Brahman to be the place of deep sleep; and hence there is a doubt whether each of them in turns, or all of them together, are that place. There is an option between them, since they are not in mutual dependence, and since the sleeping soul cannot at the same time be in several places!—To this the Sūtra replies—the absence of dreams, i.e. deep sleep takes place in the veins, in the pericardium, and in the highest Self together; since these three are declared by Scripture. When different alternatives may be combined, on the ground of there being different effects in each case, it is improper to assume an option which implies sublation of some of the alternatives. And in the present case such combination is possible, the veins and the pericardium holding the position of a mansion, as it were, and a couch within the mansion, while Brahman is the pillow, as it were. Thus Brahman alone is the immediate resting-place of the sleeping soul.