Śatapatha Brāhmaṇa ("of a hundred paths") 6.6.4.1

6.6.4.1

atha viṣṇukramānkrāntvā | vātsapreṇopasthāyāstamita āditye bhasmaiva prathamamudvapatyetadvā enametenānnena prīṇātyetābhiḥ samidbhistasyānnasya jagghasyaiṣa pāpmā sīdati bhasma tenainametadvyāvartayati tasminnapahatapāpmanvācaṃ visṛjate vācaṃ visṛjya samidhamādadhāti rātryā evainametadannena prīṇāti rātrīṃ-rātrīmaprayāvam bharanta iti tasyokto bandhū rātryā evaitāmariṣṭiṃ svastimāśāste tadyatkiṃ cātī rātryopasamādadhātyāhutikṛtaṃ haivāsmai tadupasamādadhāti

Having then stridden the Vishnu strides, and reverentially stood by (the fire) with the Vâtsapra (hymn), after the sun has set, he in the first place throws out the ashes (from the fire-pan). For at that (former) time he regales him (Agni) with that food, those kindling-sticks; and the foul part of that eaten food sinks to the bottom as ashes. He now clears him thereof, and infuses speech into him, thus freed from foulness. Having infused speech, he puts on a kindling-stick,--and thereby regales him with food for the night,--with, 'Night for night bearing unremittingly '--the meaning of this has been told: he prays for that same security and wellbeing for the night; and whatsoever he puts on 'thereafter by night, that he puts on as a libation offered to him.