Śatapatha Brāhmaṇa ("of a hundred paths") 8.4.2.6

8.4.2.6

mitrasya bhāgo 'si | varuṇasyādhipatyamiti prāṇo vai mitro 'pāno varuṇaḥ prāṇāya bhāgaṃ kṛtvāpānāyādhipatyamakaroddivo vṛṣṭirvāta spṛta ekaviṃśa stoma iti vṛṣṭiṃ ca vātaṃ ca prajānāmekaviṃśena stomena pāpmano mṛtyoraspṛṇot

'Mitra's share thou art, Varuna s lordship!'--Mitra, doubtless, is the out-breathing, and Varuna the down-breathing: having bestowed a share on the out-breathing, he bestowed lordship on the down-breathing;--'heaven's rain, the wind is freed; the Ekavimsa-stoma!'--by means of the twenty-one-fold hymn-form he frees both rain and wind for living beings from evil, from death.