Katha Upanishad - Verse 2.2.3
Text: ऊर्ध्वं प्राणमुन्नयत्यपानं प्रत्यगस्यति । मध्ये वामनमासीनं विश्वे देवा उपासते ॥ ३ ॥ ūrdhvaṃ prāṇamunnayatyapānaṃ pratyagasyati | madhye vāmanamāsīnaṃ viśve devā upāsate || 3 || 3. He leads the prana upwards and casts the apana downwards; the dwarf seated in the middle, all Devas worship. Shankara’s Commentary: Com.—In realising the existence of the atman an evidence is offered—Upwards] from the heart. Praba the wind, whose function is connected with breath. Unnayati ] leads upwards....