Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.3.6

8.2.3.6

yadvevāpasyā upadadhāti | eṣvevaitatprāṇeṣvapo dadhāti tā antarhitāḥ prāṇabhṛdbhya upadadhātyanantarhitāstatprāṇebhyo 'po dadhātyatho annaṃ vā āpo 'nantarhitaṃ tatprāṇebhyo 'nnaṃ dadhātyapaḥ pinvauṣadhīrjinva dvipādava catuṣpātpāhi divo vṛṣṭimerayetyetā evaiṣvetatkLptā apo dadhāti

And, again, as to why he lays down Apasyâs,--he thereby puts water into the vital airs. He places them so as not to be separated from the Prânabhrits: he thus places the water so as not to be separate from the vital airs. Moreover, water is food: he thus introduces food not separated from (the channels of) the vital airs. [He lays them down with, Vâg. S. XIV, 8], 'Make the waters swell! Quicken the plants! Bless thou the two-footed! Protect the four-footed! Draw thou rain from the sky!' He thereby puts water that is made fit, into those (vital airs).