9 Now, the question is raised: “Since people think that they will become the Whole by knowing brahman, what did brahman know that enabled it to become the Whole?”
10 In the beginning this world was only brahman, and it knew only itself (atman), thinking: “I am brahman” As a result, it became the Whole. Among the gods, likewise, whosoever realized this, only they became the Whole. It was the same also among the seers and among humans. Upon seeing this very point, the seer Vamadeva proclaimed: “I was Manu, and I was the sun.” This is true even now. If a man knows “I am brahman” in this way, he becomes this whole world. Not even the gods are able to prevent it, for he becomes their very self (atman). So when a man venerates another deity, thinking, “He is one, and I am another,” he does not understand.
Brihadaranyaka Upanishad 9-10