Chandogya Upanishad 4.3

vāyur vāva saṃvargaḥ yadā vā agnir udvāyati vāyum evāpyeti yadā sūryo 'stam eti vāyum evāpyeti yadā candro 'stam eti vāyum evāpyeti

'Air (vâyu) is indeed the end of all. For when fire goes out, it goes into air. When the sun goes down, it goes into air. When the moon goes down, it goes into air.

yadāpa ucchuṣyanti vāyum evāpiyanti vāyur hy evaitān sarvān saṃvṛṅkte ity adhidaivatam

'When water dries up, it goes into air. Air indeed consumes them all. So much with reference to the Devas.

athādhyātmam prāṇo vāva saṃvargaḥ sa yadā svapiti prāṇam eva vāg apyeti prāṇaṃ cakṣuḥ prāṇaṃ śrotram prāṇaṃ manaḥ prāṇo hy evaitān sarvān saṃvṛṅkta iti

'Now with reference to the body. Breath (prâna) is indeed the end of all. When a man sleeps, speech goes into breath, so do sight, hearing, and mind. Breath indeed consumes them all.

tau vā etau dvau saṃvargau vāyur eva deveṣu prāṇaḥ prāṇeṣu

'These are the two ends, air among the Devas, breath among the senses (prâna).'

atha ha śaunakaṃ ca kāpeyam abhipratāriṇaṃ ca kākṣaseniṃ pariviṣyamāṇau brahmacārī bibhikṣe tasmā u ha na dadatuḥ

Once while Saunaka Kâpeya and Abhipratârin Kâkshaseni were being waited on at their meal, a religious student begged of them. They gave him nothing.

sa hovāca mahātmanaś caturo deva ekaḥ kaḥ sa jagāra bhuvanasya gopāḥ taṃ kāpeya nābhipaśyanti martyā abhipratārin bahudhā vasantam yasmai vā etad annaṃ tasmā etan na dattam iti

He said; 'One god— who is he?— swallowed the four great ones, he, the guardian of the world. O Kâpeya, mortals see him not, O Abhipratârin, though he dwells in many places. He to whom this food belongs, to him it has not been given.'

tad u ha śaunakaḥ kāpeyaḥ pratimanvānaḥ pratyeyāya ātmā devānāṃ janitā prajānāṃ hiraṇyadaṃṣṭro babhaso 'nasūriḥ mahāntam asya mahimānam āhur anadyamāno yad anannam atti iti vai vayam brahmacārin nedam upāsmahe dattāsmai bhikṣām iti

Saunaka Kâpeya, pondering on that speech, went to the student and said: 'He is the self of the Devas, the creator of all beings, with golden tusks, the eater, not without intelligence. His greatness is said to be great indeed, because, without being eaten, he eats even what is not food. Thus do we, O Brahmakârin, meditate on that Being.' Then he said: 'Give him food.'

tasmai u ha daduḥ te vā ete pañcānye pañcānye daśa santas tat kṛtam tasmāt sarvāsu dikṣv annam eva daśa kṛtam saiṣā virāḍ annādī tayedaṃ sarvaṃ dṛṣṭam sarvam asya idaṃ dṛṣṭaṃ bhavaty annādo bhavati ya evaṃ veda ya evaṃ veda

They gave him food. Now these five (the eater Vâyu (air), and his food, Agni (fire), Âditya (sun), Kandramas (moon), Ap (water)) and the other five (the eater Prâna (breath), and his food, speech, sight, hearing, mind) make ten, and that is the Krita. (the highest) cast (representing the ten, the eaters and the food). Therefore in all quarters those ten are food (and) Krita. (the highest cast). These are again the Virâg (of ten syllables) which eats the food. Through this all this becomes seen. He who knows this sees all this and becomes an eater of food, yea, he becomes an eater of food.