Śatapatha Brāhmaṇa ("of a hundred paths") 7.1.2.21

7.1.2.21

saiṣā tredhāvihitā vāganṛṣṭup | tāmeṣo 'gniḥ prāṇo bhūtvānusaṃcarati ya āhavanīye 'gniḥ sa prāṇaḥ so 'sāvādityo 'tha ya āgnīdhrīye 'gniḥ sa vyānaḥ sa u ayaṃ vāyuryo 'yam pavate 'tha yo gārhapatye 'gniḥ sa udānaḥ sa u ayaṃ yo 'yamasmiṃloke 'gnirevaṃviddha vāva sarvāṃ vācaṃ sarvam prāṇaṃ sarvamātmānaṃ saṃskurute

That same Anushtubh, speech, is threefold. That fire, taking the form of the vital air, goes along with it (speech),--the fire which is on the Âhavanîya (altar) is the out-breathing, and yonder sun; and the fire which is on the Âgnîdhrîya is the through-breathing, and the wind which blows yonder; and the fire which is on the Gârhapatya is the in-breathing, and what fire there is here in this (earth-) world. And verily he who knows this makes up for himself the whole Vâk (speech), the whole vital air, the whole body (of Pragâpati).