Śatapatha Brāhmaṇa ("of a hundred paths") 3.6.1.28

3.6.1.28

sarve ha sma vā ete purā jvalanti | yathāyamāhavanīyo yathā gārhapatyo yathāgnīdhrīyastadyata enānudavāpayaṃstata evaitanna jvalanti tānāgnīdhramabhi saṃrurudhustānapyardhamāgnīdhrasya jigyustato viśve devā amṛtatvamapājayaṃstasmādvaiśvadevam

For, indeed, all of those (hearths) at one time burnt as brightly as this Âhavanîya and the Gârhapatya and the Âgnîdhrîya; but ever since that time when they (the Asuras) overturned them they do not burn. They forced them (the gods) back to the Âgnîdhra (fire) and even won from them one half of the Âgnîdhra. From there the All-gods gained immortality,--whence it (the Âgnîdhra fire) is sacred to the All-gods.