Śatapatha Brāhmaṇa ("of a hundred paths") 6.4.4.2

6.4.4.2

so 'śvamabhimantrayate | sa jāto garbho asi rodasyoritīte vai dyāvāpṛthivī rodasī tayoreṣa jāto garbho 'gne cārurvibhṛta oṣadhīṣviti sarvāsu hyeṣa cārurvibhṛta oṣadhiṣu citraḥ śiśuḥ pari tamāṃsyaktūniti citro vā eṣa śiśuḥ pareṇa tamāṃsyaktūnatirocate pra mātṛbhyo adhi kanikradadgā ityoṣadhayo vā etasya mātarastābhya eṣa kanikradatpraiti tadaśve vīryaṃ dadhāti

He addresses the horse, with (Vâg. S. XI, 43 Rik S. X, 1, 2), 'Thus born, art thou the child of the two worlds;'--the two worlds, doubtless, are these two, heaven and earth; and he (Agni) thus born, is the child of these two;--'O Agni, the lovely (child), distributed among the plants,'--for he, the lovely one, is indeed distributed among all the plants;--'a brilliant child, through gloom and night,'--for as a brilliant child, he (Agni) indeed shines beyond gloom and night;--'crying aloud thou didst go forth from the mothers;'--his mothers, doubtless, are the plants, and from them he comes forth crying aloud. He thereby lays vigour into the horse.