Chandogya Upanishad 4.14

te hocuḥ upakosalaiṣā somya te 'smadvidyātmavidyā ca ācāryas tu te gatiṃ vakteti ājagāma hāsyācāryaḥ tam ācāryo 'bhyuvādopakosala3 iti

Then they all said: 'Upakosala, this is our knowledge, our friend, and the knowledge of the Self, but the teacher will tell you the way (to another life).'

bhagava iti ha pratiśuśrāva brahmavida iva somya mukhaṃ bhāti ko nu tvānuśaśāseti ko nu mānuśiṣyād bho itīhāpeva nihnute ime nūnam īdṛśā anyādṛśā itīhāgnīn abhyūde kiṃnu somya kila te 'vocann iti

In time his teacher came back, and said to him: 'Upakosala.' He answered: 'Sir.' The teacher said: 'Friend, your face shines like that of one who knows Brahman. Who has taught you?' 'Who should teach me, Sir?' he said. He denies, as it were. And he said (pointing) to the fires: 'Are these fires other than fires?' The teacher said: 'What, my friend, have these fires told you?'

idam iti ha pratijajñe lokān vāva kila somya te 'vocan ahaṃ tu te tad vakṣyāmi yathā puṣkarapalāśa āpo na śliṣyanta evam evaṃvidi pāpaṃ karma na śliṣyata iti bravītu me bhagavān iti tasmai hovāca

He answered: 'This' (repeating some of what they had told him). The teacher said: 'My friend, they have taught you about the worlds, but I shall tell you this; and as water does not cling to a lotus leaf, so no evil deed clings to one who knows it.' He said: 'Sir, tell it me.'