Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.9.16

4.6.9.16

te yathādhiṣṇyamevopaviśanti | devebhyo ha vai vāco raso 'bhijito 'pacikramiṣāṃ cakāra sa imāmeva parāṅatyasisṛpsadiyaṃ vai vāktasyā eṣa raso yadoṣadhayo yadvanaspatayastametena sāmnāpnuvantsa enānāpto 'bhyāvartata tasmādasyāmūrdhvā oṣadhayo jāyanta ūrdhvā vanaspatayastatho evaitebhya etadvāco raso 'bhijito 'pacikramiṣati sa imāmeva parāṅatisisṛpsatīyaṃ vai vāktasyā eṣa raso yadoṣadhayo yadvanaspatayastametena sāmnāpnuvanti sa enānāpto 'bhyāvartate tasmādasyāmūrdhvā oṣadhayo jāyanta ūrdhvā vanaspatayaḥ

They sit down by their several dhishnya-hearths. Now, once on a time, the pith of Vâk (speech) wished to desert the gods who had won it; it tried to creep away along this earth, for Vâk is this earth: her pith are these plants and trees. By means of this Sâman they overtook it, and, thus overtaken, it returned to them. Hence upwards on this earth grow the plants, and upwards the trees. And in like manner does the pith of Vâk wish to desert these (sacrificers) who have won it, and tries to creep away along this earth,--for Vâk is this earth: her pith are these plants and trees. By means of this Sâman they overtake it, and, thus overtaken, it returns to them. Hence upwards on this earth grow the plants, and upwards the trees.