Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 2.1.2

2.1.2

sa hovāca gārgyo ya evāsāvāditye puruṣa etamevāhaṃ brahmopāsa iti sa hovācājātaśatrurmā maitasminsaṃvadiṣṭhā atiṣṭhāḥ sarveṣāṃ bhūtānāṃ mūrdhā rājeti vā ahametamupāsa iti sa ya etamevamupāste'tiṣṭhāḥ sarveṣāṃ bhūtānāṃ mūrdhā rājā bhavati

Gârgya said: 'The person that is in the sun, that I adore as Brahman.' Agâtasatru said to him: 'No, no! Do not speak to me on this. I adore him verily as the supreme, the head of all beings, the king. Whoso adores him thus, becomes Supreme, the head of all beings, a king.'