Shatapatha Brahmana 10.1.4.14

10.1.4.14

tadāhuḥ kiṃ tadagnau kriyate yena yajamānaḥ punarmṛtyumapajayatītyagnirvā eṣa devatā bhavati yo'gniṃ cinute'mṛtamu vā agniḥ śrīrdevāḥ śriyaṃ gacati yaśo devā yaśo ha bhavati ya evaṃ veda

Here, now, they say, 'What is done here in (the building of) the altar, whereby the Sacrificer conquers recurring death?' Well, he who builds an altar becomes the deity Agni; and Agni (the fire), indeed, is the immortal (element);--the gods are splendour: he enters splendour; the gods are glory: he becomes glorious whosoever knows this.