The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
30. The declaration (made by Indra about himself, viz. that he is one with Brahman) (is possible) through intuition vouched for by Scripture, as in the case of Vâmadeva.
The individual divine Self called Indra perceiving by means of rishi-like intuition 1--the existence of which is vouched for by Scripture--its own Self to be identical with the supreme Self, instructs Pratardana (about the highest Self) by means of the words 'Know me only.'
By intuition of the same kind the rishi Vâmadeva reached the knowledge expressed in the words, 'I was Manu and Sûrya;' in accordance with the passage, 'Whatever deva was awakened (so as to know Brahman) he indeed became that' (Bri. Up. I, 4, 10). The assertion made above (in the pûrvapaksha of the preceding Sûtra) that Indra after saying, 'Know me only,' glorifies himself by enumerating the slaying of Tvashtri's son and other deeds of strength, we refute as follows. The death of Tvashtri's son and similar deeds are referred to, not to the end of glorifying Indra as the object of knowledge--in which case the sense of the passage would be, 'Because I accomplished such and such deeds, therefore know me'--but to the end of glorifying the cognition of the highest Self. For this reason the text, after having referred to the slaying of Tvashtri's son and the like, goes on in the clause next following to exalt knowledge, 'And not one hair of me is harmed there. He who knows me thus by no deed of his is his life harmed.'--(But how does this passage convey praise of knowledge?)--Because, we reply, its meaning is as follows: 'Although I do such cruel deeds,
yet not even a hair of mine is harmed because I am one with Brahman; therefore the life of any other person also who knows me thus is not harmed by any deed of his.' And the object of the knowledge (praised by Indra) is nothing else but Brahman which is set forth in a subsequent passage, 'I am prâna, the intelligent Self.' Therefore the entire chapter refers to Brahman.
101:1 I.e. spontaneous intuition of supersensible truth, rendered possible through the knowledge acquired in former existences.