Śatapatha Brāhmaṇa ("of a hundred paths") 3.7.4.4

3.7.4.4

sa prokṣati | adbhyastvauṣadhībhya iti tadyata eva sambhavati tata evaitanmedhyaṃ karotīdaṃ hi yadā varṣatyathauṣadhayo jāyanta oṣadhīrjagdhvāpaḥ pītvā tata eṣa rasaḥ sambhavati rasādreto retasaḥ paśavastadyata eva sambhavati yataśca jāyate tata evaitanmedhyaṃ karoti

He sprinkles with, 'For the waters--thee, for the plants!' whereby it (the victim) exists, thereby he thus makes it sacrificially pure. For when it rains, then plants are produced here on earth; and by eating plants and drinking water that sap originates, and from sap seed, and from seed beasts: hence whereby it exists, wherefrom it springs, thereby he thus makes it sacrificially pure.