Khandogya-Upanishad: Sixth Prapathaka, Eighth Khanda

“When a man sleeps here, then, my dear son, he becomes united with the True, he is gone to his own (Self). Therefore they say, svapiti, he sleeps, because he is gone (apita) to his own (sva).

2. “As a bird when tied by a string flies first in every direction, and finding no rest anywhere, settles down at last on the very place where it is fastened, exactly in the same manner, my son, that mind (the giva, or living Self in the mind, see VI, 3, 2), after flying in every direction, and finding no rest anywhere, settles down on breath; for indeed, my son, mind is fastened to breath.

3. “Learn from me, my son, what are hunger and thirst. When a man is thus said to be hungry, water is carrying away (digests) what has been eaten by him. Therefore as they speak of a cow-leader (go-naya), a horse-leader (asva-naya), a man-leader (purusha-naya), so they call water (which digests food and causes hunger) food-leader (asa-naya). Thus (by food digested &c.), my son, know this offshoot (the body) to be brought forth, for this (body) could not be without a root (cause).

4. “And where could its root be except in food (earth)? And in the same manner, my son, as food (earth) too is an offshoot, seek after its root, viz. water. And as water too is an offshoot, seek after its root, viz. fire. And as fire too is an offshoot, seek after its root, viz. the True. Yes, all these creatures, my son, have their root in the True, they dwell in the True, they rest in the True.

5. “When a man is thus said to be thirsty, fire carries away what has been drunk by him. Therefore as they speak of a cow-leader (go-naya), of a horse-leader (asva-naya), of a man-leader (purusha-naya), so they call fire udanyi, thirst, i.e. water-leader. Thus (by water digested &c.), my son, know this offshoot (the body) to be brought forth: this (body) could not be without a root (cause).

6. “And where could its root be except in water? As water is an offshoot, seek after its root, viz. fire. As fire is an offshoot, seek after its root, viz. the True. Yes, all these creatures, O son, have their root in the True, they dwell in the True, they rest in the True.

“And how these three beings (devata), fire, water, earth, O son, when they reach man, become each of them tripartite, has been said before (VI, 4, 7). When a man departs from hence, his speech is merged in his mind, his mind in his breath, his breath in heat (fire), heat in the Highest Being.

7. “Now that which is that subtile essence (the root of all), in it all that exists has its self. It is the True. It is the Self, and thou, O Svetaketu, art it.”

“Please, Sir, inform me still more,” said the son.

“Be it so, my child,” the father replied.