Śatapatha Brāhmaṇa ("of a hundred paths") 8.6.3.17

8.6.3.17

yadveva punaścitimupadadhāti | yaṃ vai tam prāṇā ṛṣayo 'gre 'gniṃ samaskurvantsa eṣa tamevaitatpunaścinoti tadyaccitaṃ santam punaścinoti tasmādveva punaścitiḥ

And, again, as to why he lays down the Punaskiti. This (altar), doubtless, is that same Agni whom in the beginning the vital airs, the Rishis, made up. He now builds him up again; and inasmuch as he again (punas) builds up (ki) that (Agni) already built, therefore also it is (called) Punaskiti.