Maitrayaniya Upanishad 2.5.6

2.5.6

pratyaṅgaṃ śarīrasya samānayati samyag āsamantānnayati prāpayatyeṣa vāva sa samānasañjñā samānasañjña ityarthaḥ | samānavyānayormadhye udānasyoddeśe kāraṇaṃ sūcayannudānasyābhivyaktisthānamāha uttaramiti | eteṣāṃ prāṇāpānasamānānāmuttaramupari eteṣāṃ samyagvyāpārānantaraṃ vyānasya rūpañca vyānavyāpāraścāntarā madhye, prasūtiḥ prasavo'bhivyaktirevodānasya antarevetyevakāro'bhinnakramaḥ | ukta eva cānvayaḥ | ayamarthaḥ prāṇāpānābhyāmucchvāsaniśvasābhyāṃ dhamyamāno hi jāṭharo'gnirannaṃ bhuktaṃ pacati tat pākanirvṛttañca samāno vibhajya samaṃ nayati | evamaśitapītayoḥ samaṃ nītayoḥ satoḥ kṣudutpadyate pipāsā ca, tadodāna udbhūtavṛttirāsyagataṃ yatkiñcinnigirati pittodrekavaśādgodgirati hṛdayādigataṃ kaphādikaṃ tato dehe balapuṣṭyādyādhānaṃ vyānavāyoḥ kṛtaṃ bhavati | evamuktaprakāreṇa pūrveṣāṃ caturṇāṃ vāyuvyāpārāṇāṃ yathāvadvinivṛttau vyānasya sañcāramauṣṭhavābhāvāddehe balapuṣṭyādayo na jāyante ityetadanubhavasiddhaṃ śāstrasiddhañca, ato yukto'yaṃ kramanirdeśa iti | atha yo'yaṃ pītāśitaṃ pītañcāśitañca pītāśitaṃ tadudgirati ūrddhaṃ niḥsārayati, nigirati vā nīcairgirati tīrodadhātīti vā eṣa vāva sa udānaṃ iti