Śatapatha Brāhmaṇa ("of a hundred paths") 7.2.3.2

7.2.3.2

yadveva darbhastambamupadadhāti | jāyata eṣa etadyaccīyate sa eṣa sarvasmā annāya jāyata ubhayamvetadannaṃ yaddarbhā āpaśca hyetā oṣadhayaśca yā vai vṛtrādbībhatsamānā āpo dhanva dṛbhantya udāyaṃste darbhā abhavanyaddvabhantya udāyaṃstasmāddarbhāstā haitāḥ śuddhā medhyā āpo vṛtrābhiprakṣaritā yaddarbhā yadu darbhāstenauṣadhaya ubhayenaivainmetadannena prīṇāti

And, again, why he places a bunch of grass thereon;--when he (Agni) is built up, he is born, and he is born here for all (kinds of) food; but these darbha plants (contain) both kinds of food, for they are both water and plants. Now the waters which, loathing Vritra, rose up on the dry land forming bushes, became those grasses,--inasmuch as they rose forming bushes (dribh), they are (called) darbha-grasses. These darbha-grasses, then, are the water (which remained) pure, and meet for sacrifice, when Vritra flowed towards it; and inasmuch as they are darbha-grasses, they are plants: by both kinds of food he thus gratifies him (Agni).