Shatapatha Brahmana 10.4.1.9

10.4.1.9

taddhaitatpaśyannṛṣirabhyanūvāda bhūtam bhaviṣyatprastaumi mahadbrahmaikamakṣaram bahu brahmaikamakṣaramityetaddhyevākṣaraṃ sarve devāḥ sarvāṇi bhūtānyabhisampadyante tadetadbrahma ca kṣatraṃ cāgnireva brahmendraḥ kṣatramindrāgnī vai viśve devā viḍu viśve devāstadetadbrahma kṣatraṃ viṭ

It is this that the Rishi saw when he said, 'I praise what hath been and what will be, the Great Brahman, the one Akshara,--the manifold Brahman, the one Akshara; for, indeed, all the gods, all beings pass into that Akshara (imperishable element): it is both the Brahman and the Kshatra; and the Brahman is Agni, and the Kshatra Indra; and the Visve Devâh (all the gods) are Indra and Agni.' But the Visve Devâh (the All-gods) are also the peasantry: hence it is Priesthood, Nobility, and Peasantry.