Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 1.4.11

1.4.11

brahma vā idamagra āsīdekameva tadekam̐ sanna vyabhavat | tacchreyorūpamatyasṛjata kṣatraṃ yānyetāni devatrā kṣatrāṇīndro varuṇaḥ somo rudraḥ parjanyo yamo mṛtyurīśāna iti tasmātkṣatrātparaṃ nāsti tasmādbrāhmaṇaḥ kṣatriyamadhastādupāste rājasūye kṣatra eva tadyaśo dadhāti saiṣā kṣatrasya yoniryadbrahma | tasmādyadyapi rājā paramatāṃ gacchati brahmaivāntata upaniśrayati svāṃ yoniṃ ya u enam̐ hinasti svām̐ sa yonimṛcchati sa pāpīyān bhavati yathā śreyām̐sam̐ him̐sitvā

Verily in the beginning this was Brahman, one only. That being one, was not strong enough. It created still further the most excellent Kshatra (power), viz. those Kshatras (powers) among the Devas,--Indra, Varuna, Soma, Rudra, Parganya, Yama, Mrityu, Îsâna. Therefore there is nothing beyond the Kshatra, and therefore at the Râgasûya sacrifice the Brâhmana sits down below the Kshatriya. He confers that glory on the Kshatra alone. But Brahman is (nevertheless) the birth-place of the Kshatra. Therefore though a king is exalted, he sits down at the end (of the sacrifice) below the Brahman, as his birth-place. He who injures him, injures his own birth-place. He becomes worse, because he has injured one better than himself.