Jaiminīya (Talavakāra) Brāhmaṇa 2-5.168

2-5.168

tasya vāmadevyaṃ pṛṣṭhaṃ bhavati svāram
svārāṇi sarvāṇi sāmānyavakalpayanti
prāṇo vai svaraḥ
prāṇaireva tatprāṇānudgātā yajamānasya nisvarati
tadāhuryajñāyajñīyasya stotre jaghanena gārhapatyaṃ dakṣiṇā prāvṛtya nipadyeta
tata eva svargaṃ lokametīti
tadu vā āhurvikarṣo vai tathā yajñasya bhavati yadasaṃsthite nipadyeta
yadaiva sarvaṃ karma saṃtiṣṭheta yadā vaśayā careyuḥ
atha jaghanenāhavanīyaṃ dakṣiṇā prāvṛtya nipadyeta
tata eva svargaṃ lokametīti
asau vā āditya āhavanīyaḥ
eṣa vai svargo lokaḥ
etasminneva tata svarge loke'ntata pratitiṣṭhati

Its pṛṣṭha is the Vāmadevya [sāman] with a finale (svāram).
They arrange all the sāmans as svāras.
Sound (svara) is breath.
By means of breaths, the Udgātṛ sounds out the breaths of the sacrificer.
Concerning this they say: 'At the stotra of the Yajñāyajñīya, he should lie down behind the Gārhapatya, turned toward the south.
From there he goes to the heavenly world.'
Regarding this they also say: 'That would be a disconnection of the sacrifice, if he were to lie down while [the rite] is unfinished.
Only when the whole ritual act has been completed, when they proceed with the barren cow,
then, having turned toward the south behind the Āhavanīya, he should lie down.
From there he goes to the heavenly world.'
Yonder Āhavanīya is Āditya (the sun).
This indeed is the heavenly world.
In that very heavenly world he ultimately firmly establishes himself.