Brihadaranyaka Upanishad 4.1.4

4.1.4

yadeva te kaścida-bravīttacchṛṇavāmetyabravīnme barkurvārṣṇaścakṣurvai brahmetiyathā mātṛmānpitṛmā-nācāryavānbrūyāttathā tadvārṣṇo'bravīccakṣurvai brahmetyapaśyato hi kim̐ syādi-tyabravīttu te tasyāyatanaṃ pratiṣṭhaṃ na me'bravīdityekapādvā etatsamrāḍiti sa vai no brūhi yājñavalkya cakṣurevāyatanamākāśaḥ pratiṣṭhā satyamityenadupāsīta kā satyatā yājñavalkya cakṣureva samrāḍiti hovāca cakṣuṣā vai samrāṭpaśya-ntamāhuradrākṣīriti sa āhādrākṣamiti tatsatyaṃ bhavati cakṣurvaisamrāṭparamaṃ brahma nainaṃ cakṣurjahāti sarvāṇyenaṃ bhūtānyabhikṣaranti devo bhūtvādevānapyeti ya evaṃ vidvānetadupāste hastyṛṣabham̐ sahasraṃ dadāmīti hovāca janako vaidehaḥ sa hovāca yājñavalkyaḥ pitā me'manyata nānanuśiṣyahareteti

'Let me hear whatever anyone may have told you.' 'Barku, the son of Vriṣhṇa, has told me that the eye (sun) is Brahman.' 'As one who has a mother, father and teacher should say, so has the son of Vriṣhṇa said this—that the eye is Brahman. For what can a person have who cannot see? But did he tell you about its abode and support?' 'No, he did not.' 'This Brahman is only one-footed, O Emperor.' 'Then you tell us, Yājñavalkya.' 'The eye is its abode, and the ether (Undifferentiated) its support. It should be meditated upon as truth.' 'What is truth, Yājñavalkya?' 'The eye itself, O Emperor,' said Yājñavalkya, 'if a person, O Emperor, says to one who has seen with the eyes, "Have you seen?" and one answers, "Yes, I have," then it is true. The eye, O Emperor, is the Supreme Brahman. The eye never leaves him who knowing thus meditates upon it, all beings eagerly come to him, and being a god, he attains the gods.' 'I give you a thousand cows with a bull like an elephant,' said Emperor Janaka. Yājñavalkya replied, 'My father was of opinion that one should not accept (wealth) from a disciple without fully instructing him.'