4.29

अपाने जुह्वति प्राणं प्राणेऽपानं तथापरे ।
प्राणापानगती रुद्ध्वा प्राणायामपरायणाः ॥

apāne juhvati prāṇaṃ prāṇe 'pānaṃ tathāpare
prāṇāpānagatī ruddhvā prāṇāyāmaparāyaṇāḥ

Kṛṣṇa (कृष्ण) is still speaking, to Arjuna.

The verse

Others, given over to restraint of the breath, offer the prāṇa (प्राण) into the apāna (अपान) and the apāna (अपान) into the prāṇa (प्राण), having checked the two courses.

नेपालीमा

श्वास रोक्न लागेका अरूहरूले दुई चाल रोकेर प्राणलाई अपानमा र अपानलाई प्राणमा चढाउँछन्।

Where it sits

4.27 offered the actions of the breaths into a yoga-fire, and this verse makes the breaths the sacrifice itself, each poured into the other. 4.30 adds measured food, and then says what all of these people are.

Split: अपाने + जुह्वति + प्राणम् + प्राणे + अपानम् + तथा + अपरे + प्राण-अपान-गती + रुद्ध्वा + प्राणायाम-परायणाः

apāne + juhvati + prāṇam + prāṇe + apānam + tathā + apare + prāṇa-apāna-gatī + ruddhvā + prāṇāyāma-parāyaṇāḥ

Sanskrit, in depth

The words

देवनागरीWordGrammarSense
अपानेapānelocative singularin the apāna (अपान), the downward breath.
जुह्वतिjuhvatipresent, 3rd pluralthey offer.
प्राणम्prāṇamaccusativethe prāṇa (प्राण), the breath that moves the other way.
प्राणेprāṇelocative singularin the prāṇa (प्राण).
अपानम्apānamaccusativethe apāna (अपान).
तथाtathāindeclinableand so, likewise.
अपरेaparenominative pluralothers.
प्राण-अपान-गतीprāṇa-apāna-gatīaccusative dualthe two courses, of prāṇa (प्राण) and of apāna (अपान). gati (गति) is a going. The dual ending is --ī (ई).
रुद्ध्वाruddhvāgerundhaving checked, having held. From rudh (रुध्).
प्राणायाम-परायणाःprāṇāyāma-parāyaṇāḥnominative plural, bahuvrīhi (बहुव्रीहि)those whose resort is restraint of the breath. prāṇāyāma (प्राणायाम) is that restraint. parāyaṇa (परायण) is the final recourse.

The phrases

apāne juhvati prāṇam (अपाने जुह्वति प्राणम्) is the first pour. They offer the prāṇa (प्राण) into the apāna (अपान). Locative is the fire, the place offered into. Accusative is what is poured.

prāṇe apānam tathā apare (प्राणे अपानम् तथा अपरे) is the reverse pour. And likewise others offer the apāna (अपान) into the prāṇa (प्राण). prāṇe apānam (प्राणे अपानम्) is prāṇe 'pānam (प्राणेऽपानम्). tathā apare (तथा अपरे) is tathāpare (तथापरे). The subject apare (अपरे) is late, and it covers both offerings.

prāṇāpānagatī ruddhvā prāṇāyāmaparāyaṇāḥ (प्राणापानगती रुद्ध्वा प्राणायामपरायणाः) is how. Having checked the two courses, they are people given over to breath-restraint. The gerund ruddhvā (रुद्ध्वा) belongs to apare (अपरे).

Sanskrit in this line

apāne (अपाने) and prāṇe (प्राणे) are locative, the place offered into. prāṇam (प्राणम्) and apānam (अपानम्) are accusative, the thing offered. The verse swaps them. Do not give both breaths the same case. prāṇe 'pānam (प्राणेऽपानम्) is ए + अ e + a, the avagraha of 4.3: the e (ए) stays, the a (अ) of apānam (अपानम्) drops.

Say it back

Which breath is poured into which, both ways. If you name only one direction, stay here.