Chandogya Upanishad 6.14

yathā somya puruṣaṃ gandhārebhyo 'bhinaddhākṣam ānīya taṃ tato 'tijane visṛjet sa yathā tatra prāṅ vodaṅ vā adharāṅ vā pratyaṅ vā pradhmāyītābhinaddhākṣa ānīto 'bhinaddhākṣo visṛṣṭaḥ

'As one might lead a person with his eyes covered away from the Gandhâras, and leave him then in a place where there are no human beings; and as that person would turn towards the east, or the north, or the west, and shout, "I have been brought here with my eyes covered, I have been left here with my eyes covered,"

tasya yathābhinahanaṃ pramucya prabrūyād etāṃ diśaṃ gandhārā etāṃ diśaṃ vrajeti sa grāmād grāmaṃ pṛcchan paṇḍito medhāvī gandhārān evopasaṃpadyeta evam evehācāryavān puruṣo veda tasya tāvad eva ciraṃ yāvan na vimokṣye 'tha sampatsya iti

'And as thereupon some one might loose his bandage and say to him, "Go in that direction, it is Gandhâra, go in that direction;" and as thereupon, having been informed and being able to judge for himself, he would by asking his way from village to village arrive at last at Gandhâra,—in exactly the same manner does a man, who meets with a teacher to inform him, obtain the true knowledge. For him there is only delay so long as he is not delivered (from the body); then he will be perfect.

sa ya eṣo 'ṇimaitad ātmyam idaṃ sarvam tat satyam sa ātmā tat tvam asi śvetaketo iti bhūya eva mā bhagavān vijñāpayatv iti tathā somyeti hovāca

'That which is the subtile essence, in it all that exists has its self. It is the True. It is the Self, and thou, O Svetaketu, art it.' 'Please, Sir, inform me still more,' said the son. 'Be it so, my child,' the father replied.