Shatapatha Brahmana 2.3.2.12

2.3.2.12

atha yatraitatpratitarāmiva | tiraścīvārciḥ saṃśāmyato bhavati tarhi haiṣa bhavati mitraḥ sa yaḥ kāmayeta maitreṇedamannamadyāmiti yamāhuḥ sarvasya vā ayam brāhmaṇo mitraṃna vā ayaṃ kaṃ cana hinastīti tarhi ha sa juhuyātprāpnoti haivaitadannādyaṃ ya evaṃ vidvāṃstarhi juhoti

And when the flame of the waning (fire) gets lower and lower, and (burns) as it were sideways, then, indeed, that (fire) is Mitra. And if any one desires to consume food here through the kindness (maitra, of others),--as one of whom they say, 'Truly, this Brahman is everybody's friend, he harms not any one,'--let him offer (the Agnihotra) then: and, assuredly, he who, knowing this, offers then (when the fire gets low), obtains that food.