Brihadaranyaka Upanishad 4.1.3

4.1.3

yadeva te kaścidabrabīttacchṛṇavāmetyabravīnma udaṅkaḥ śaulbāyanaḥprāṇo vai brahmeti yathā mātṛmānpitṛmānācāryavānbrūyāttathā tacchaulbāyano'bravītprāṇo vai brahmetya-prāṇato hi kim̐ syādityabravīttu te tasyāyatanaṃ pratiṣṭhāṃ name'bravīdityekapādvā etatsamrāḍiti sa vai no brūhi yājñavalkya prāṇa evāyatanamākāśaḥ pratiṣṭhā priyamityenadupāsīta kā priyatā yājñavalkya prāṇa eva samrāḍiti hovāca prāṇasya vai samrāṭkāmāyāyājyaṃ yājayatyapratigṛhyasyapratigṛhṇātyapi tatra vadhā-śaṅke bhavati yāṃ diśameti prāṇasyaiva samrāṭkāmāya prāṇo vai samrāṭparamaṃ brahma nainaṃ prāṇo jahāti sarvāṇyenaṃ bhūtānyabhikṣaranti devo bhūtvā devānapyeti ya evaṃ vidvānetadupāste hastyṛṣabham̐ sahasraṃ dadāmīti hovāca janako vaidehaḥ sa hovāca yājñavalkyaḥ pitā me'manyata nānanuśiṣya hareteti

'Let me hear whatever anyone may have told you.' 'Udanka, the son of Shulba, has told me that the vital force (Vāyu) is Brahman.' 'As one who has a mother, father and teacher should say, so has the son of Shulba said this—that the vital force is Brahman, for what can a person have who does not live? But did he tell you about its abode (body) and support?' 'No, he did not.' 'This Brahman is only one-footed, O Emperor.' 'Then you tell us, Yājnavalkya.' 'The vital force is its abode, and the ether (Undifferentiated) its support. It should be meditated upon as dear.' 'What is dearness, Yājnavalkya?' 'The vital force itself, O Emperor,' said Yājnavalkya, 'for the sake of the vital force, O Emperor, one performs sacrifices for one for whom they should not be performed, and accepts gifts from one from whom they should not be accepted, and it is for the sake of the vital force, O Emperor, that one runs the risk of one's life in any quarter one may go to. The vital force, O Emperor, is the Supreme Brahman. The vital force 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.'