Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.4.2

6.7.4.2

sa haiṣa dākṣāyaṇahastaḥ | yadvātsapraṃ tasmādyaṃ jātaṃ kāmayeta sarvamāyuriyāditi vātsapreṇainamabhimṛśettadasmai jātāyāyuṣyaṃ karoti tatho ha sa sarvamāyuretyatha yaṃ kāmayeta vīryavāntsyāditi vikṛtyainam purastādabhimantrayeta tatho ha sa vīryavānbhavati

Now the Vâtsapra rite, doubtless, is he, the golden-handed (Agni);--hence whomsoever that is born one may wish to obtain the full (measure of) life, let him touch that one with the Vâtsapra rite, and he thereby creates vital power for that newborn one; and accordingly that one obtains the full (measure of) life. And whomsoever one may wish to be vigorous, let him first address that one with the Vikriti (fashioning) formula, and that one accordingly becomes vigorous.