Chāndogya Upaniṣad 4.9.2

4.9.2

brahmavid iva vai somya bhāsi \
ko nu tvānuśaśāsa iti \
anye manuṣyebhya iti ha pratijajñe \
bhagavāṃs tv eva me kāme brūyāt \\409.2\

2. ‘Verily, my dear, you shine like a Brahma-knower. Who, pray, has instructed you?’ ‘Others than men,’ he acknowledged. ‘But do you yourself please speak to me; for I have heard from those who are like you, Sir, that the knowledge which has been learned from a teacher best helps one to attain his end.’ To him he then declared it. In it then nothing whatsoever was omitted—yea, nothing was omitted.