Brahman: Brihadaranyaka Upanishad 1.iv.10
Two caveats. One: the commentary is very, very short. To write down all the things I want to say about this citation requires a long paper and not a brief mail. Two: I have not checked either the citation or the reference (Brihadaranyaka upanishad - I.iv.10). I assume that both are accurate.
This (Self) was indeed Brahman in the beginning. It knew itself only as “I am Brahman.” Therefore it became …