Prashna Upanishad 16

Saḥ eṣaḥ, that very one, the eater (rises up); who is prāṇaḥ vaiśvānaraḥ, Prāṇa (life) identified with all creatures; and who is viśvarūpaḥ, possessed of all forms, being embodied in the universe. That eater, again, that is Prāṇa and agniḥ, fire; udayate, rises, every day, absorbing into himself all the cardinal points. Etat tat, this very entity, that has been referred to above; is also abhyuktam, spoken of, ṛcā, by the (following) mantra:

The enlightened realisers of Brahman knew, as their own soul, that sun that is viśvarūpam, possessed of all forms; hariṇam, full of rays; jātavedasam, endowed with enlightenment;footnote{The phrase may mean, "The knower of all that is born".} parāyaṇam, the resort of all lives; ekam jyotiḥ, the only one light, the eye, of all beings; tapantam, the radiator of heat. Who is that whom they knew? Eṣaḥ, this is; sūryaḥ, the sun; that udayati, rises;—the sun that is sahasraraśmiḥ, possessed of a thousand rays, śatadhā vartamānaḥ, that exists in a hundred (many) ways, in conformity with the difference of the creatures; and that is prāṇaḥ prajānām, the life of creatures.

It is being explained how this single pair—constituted by that which is the moon, the gross, the food (on the one hand), and that which is the formless Prāṇa, the eater, the sun (on the other)—could produce the creatures:

That very couple is the time, called saṁvatsaraḥ, the year; (and that again is) prajāpatiḥ, the Lord of creatures; for the year is brought about by that pair, the year being but a collection of the lunar days and solar days and nights, brought about by the moon and the sun. Being non-different from the food and Prāṇa, the year is said to be identical with that couple. How is that so? Tasya, of that Lord of the creatures, that the year is; there are ayane, two Courses, dakṣiṇam ca uttaram ca, the Southern and the Northern. These are the two well-known Courses, consisting each of six months, along which the sun moves to the south and the north, ordaining the results for those who perform rites alone as well as for those who undertake rites along with meditation. How is that? Tat, as to that; ye ha vai, those who; from among people, counting from the Brāhmaṇas; upāsate, follow; iṣṭāpūrte, sacrifices and public good; iti, etc.; tat, in that way; that are kṛtam, product of action, but who do not follow the uncreated Eternal—the second tat, meaning "in that way", being used adverbially:—(they) abhijayante, conquer; cāndramasam eva lokam, the very world of the moon, the world constituted by food which is a portion, called rayi (food), of the Lord of the creatures who comprises a pair. This is so because the moon is kṛta, a result of action. When the result of action is exhausted there, te eva punaḥ āvartante, it is they who come back again; for it has been said, "They enter into this or an inferior world" (Mu. I. ii. 10). Since in this way ete, these; ṛṣayaḥ, seers of heaven; prajākāmāḥ, who are desirous of progeny, the householders; attain the world of the moon—the Lord of creatures, identified with food—as the result of their sacrificial and pious acts; tasmāt, therefore; they pratipadyante, attain; dakṣiṇam, the Southern Course, that is to say, the moon, suggested by the Southern Course, the moon being itself a result of action. Eṣaḥ ha vai rayiḥ, this indeed is food; yaḥ pitryāṇaḥ, that which is the Path of the Manes, that is to say, the world of the moon, that is suggested by the term Path of the Manes.

The enlightened realisers of Brahman knew, as their own soul, that sun that is viśvarūpam, possessed of all forms; hariṇam, full of rays; jātavedasam, endowed with enlightenment;footnote{The phrase may mean, "The knower of all that is born".} parāyaṇam, the resort of all lives; ekam jyotiḥ, the only one light, the eye, of all beings; tapantam, the radiator of heat. Who is that whom they knew? Eṣaḥ, this is; sūryaḥ, the sun; that udayati, rises;—the sun that is sahasraraśmiḥ, possessed of a thousand rays, śatadhā vartamānaḥ, that exists in a hundred (many) ways, in conformity with the difference of the creatures; and that is prāṇaḥ prajānām, the life of creatures.