Śatapatha Brāhmaṇa ("of a hundred paths") 9.5.1.7

9.5.1.7

tatprātarabhipadya | abhiṣutyāgnāvajuhavustadagnāvamṛtamadadhuḥ sarveṣāmu haiṣa devānāmātmā yadagnistadyadagnāvamṛtamadadhustadātmannamṛtamadadhata tato devā amṛtā abhavan

On the morrow, having laid hold of it and pressed it (the Soma), they offered (of it) in the fire, and thereby bestowed immortality upon Agni. And he, Agni (the fire-altar), indeed, is the body of all the gods; and hence, when they bestowed immortality on Agni (the fire-altar), they bestowed immortality on their own selves, and thereby the gods became immortal.