Kaṭha Upaniṣad · 2.2.5
न प्राणेन नापानेन मर्त्यो जीवति कश्चन । इतरेण तु जीवन्ति यस्मिन्नेतावुपाश्रितौ ॥ ५ ॥
na prāṇena nāpānena martyo jīvati kaścana | itareṇa tu jīvanti yasmin netāv upāśritau || 5 ||
No one lives by prāṇa nor by apāna, oh mortal. But by another [the Ātman] they live, in whom these two are established.
This verse establishes the priority of the Ātman over the vital winds.
Na prāṇena nāpānena — neither by prāṇa nor by apāna. The vital winds are not life itself.
Martyo jīvati kaścana — no mortal lives.
Itareṇa tu jīvanti — but by another they live. The Ātman is the true vital principle.
Yasmin netāv upāśritau — in whom these two are established. The winds depend on the Ātman.
This verse is crucial for yoga: real life is the Ātman, not physiological processes. Practice must be directed toward realizing the Ātman, not only controlling the prāṇa.