Śatapatha Brāhmaṇa ("of a hundred paths") 3.9.1.19

3.9.1.19

athaindrāgnam | tejo vā agnirindriyaṃ vīryamindra ubhābhyāmeva tadvīryābhyām prajāpatiḥ punarātmānamāpyāyayatobhe enaṃ vīrye upasamāvartetāmubhe vīrye anuke ātmano kurutobhābhyāmvevaiṣa etadvīryābhyāmāpyāyata ubhe enaṃ vīrye upasamāvartete ubhe vīrye anuke ātmanaḥ kurute

And as to why it comes after that for Sarasvatî,--Sarasvatî is speech, and Soma is food: he who is incomplete by (having only) speech, now becomes indeed an eater of food.