Kaṭha Upaniṣad · 2.2.3
ऊर्ध्वं प्राणमुन्नयत्यपानं प्रत्यगस्यति । मध्ये वामनमासीनं विश्वे देवा उपासते ॥ ३ ॥
ūrdhvaṃ prāṇam unnayaty apānaṃ pratyag asyati | madhye vāmanam āsīnaṃ viśve devā upāsate || 3 ||
He elevates the prāṇa upward, casts the apāna downward; the dwarf seated in the center, all the gods adore him.
This verse describes the dynamics of the vital winds and the Ātman in the heart.
Ūrdhvaṃ prāṇam unnayati — elevates the prāṇa upward. The ascending flow of vital energy.
Apānaṃ pratyag asyati — casts the apāna downward. The exhalation, the descending flow.
Madhye vāmanam āsīnam — the dwarf seated in the center. Vāmana = the small one, the dwarf; the Ātman is diminutive but omnipotent.
Viśve devā upāsate — all the gods adore him. The senses and deities worship him.
This verse resonates with the practice of prāṇāyāma and meditation on the Ātman in the center of being.