Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.2.1

2.4.2.1

prajāpatiṃ vai bhūtānyupāsīdan | prajā vai bhūtāni vi no dhehi yathā jīvāmeti tato devā yajñopavītino bhūtvā dakṣiṇaṃ jānvācyopāsīdaṃstānabravīdyajño vo 'nnamamṛtatvaṃ va ūrgvaḥ sūryo vo jyotiriti

Now the living beings once approached Pragâpati--beings doubtless mean creatures--and said, 'Ordain unto us in what manner we are to live!' Thereupon the gods, being properly invested with the sacrificial cord and bending the right knee, approached him. To them he said, 'The sacrifice (shall be) your food; immortality your sap; and the sun your light!'