Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 4.5.7

4.5.7

brahma taṃ parādādyo'nyatrātmano brahma veda kṣatraṃ taṃ parādādyo'nyatrātmanaḥ kṣatraṃ veda lokāstaṃ parāduryo'nyatrātmano lokānveda devāstaṃ parāduryo'nyatrātmano devānveda vedāstaṃ parāduryo'nyatrātmanovedānveda bhūtāni taṃ parāduryo'nyatrātmano bhūtāni veda sarvaṃ taṃ parādādyo'nyatrātmanaḥ sarvaṃ vededaṃ brahmedaṃ kṣatramime lokā ime devā ime vedā imāni bhūtānīdam̐ sarvaṃ yadayamātmā

'Whosoever looks for the Brahman-class elsewhere than in the Self, was abandoned by the Brahman-class. Whosoever looks for the Kshatra-class elsewhere than in the Self, was abandoned by the Kshatra-class. Whosoever looks for the worlds elsewhere than in the Self, was abandoned by the worlds. Whosoever looks for the Devas elsewhere than in the Self, was abandoned by the Devas. Whosoever looks for the Vedas elsewhere than in the Self, was abandoned by the Vedas. Whosoever looks for the creatures elsewhere than in the Self, was abandoned by the creatures. Whosoever looks for anything elsewhere than in the Self, was abandoned by anything.
'This Brahman-class, this Kshatra-class, these worlds, these Devas, these Vedas, all these beings, this everything, all is that Self.