Chapter 4, Verse 29
Part of 4: Jñāna Karm Sanyās Yog — ज्ञानकर्मसंन्यासयोगअपाने जुह्वति प्राण प्राणेऽपानं तथाऽपरे। प्राणापानगती रुद्ध्वा प्राणायामपरायणाः॥
apāne juhvati prāṇaṁ prāṇe ’pānaṁ tathāpare prāṇāpāna-gatī ruddhvā prāṇāyāma-parāyaṇāḥ apare niyatāhārāḥ prāṇān prāṇeṣhu juhvati sarve ’pyete yajña-vido yajña-kṣhapita-kalmaṣhāḥ
Others offer as sacrifice the outgoing breath into the incoming, and the incoming into the outgoing, restraining the flow of the outgoing and the incoming breaths, solely absorbed in the restraint of the breath.
Some Yogis practise Puraka (inhalation), some Yogis practise Rechaka (exhalation)?,and some Yogis practise Kumbhaka (retention of breath). The five subPranas and the other Pranas are merged in the chief Prana (MukhyaPrana) by the practice of Pranayama. When the Prana is controlled, the mind also stops its wanderings and becomes steady the senses are also thinned out and merged in the Prana. It is through the vibration of Prana that the activities of the mind and the senses are kept up. If the Prana is controlled, the mind, the intellect and the senses cease to function.