Katha Upanishad - Verse 2.2.5
Text: न प्राणेन नापानेन मर्त्यो जीवति कश्चन । इतरेण तु जीवन्ति यस्मिन्नेतावुपाश्रितौ ॥ ५ ॥ na prāṇena nāpānena martyo jīvati kaścana | itareṇa tu jīvanti yasminnetāvupāśritau || 5 || 5. Not by prana, not by apana, does any mortal live; but it is by some other on which these two depend that men live. Shankara’s Commentary: The theory may be urged ‘that the body becomes destroyed only by the exit of prana, apana, etc....