Shatapatha Brahmana 7.5.1.29

7.5.1.29

tadāhuḥ | kathamasyaiṣā pakvā śṛtopahitā bhavatītiṃ yadeva yajuṣkṛtā tenātho yadvai kiṃ caitamagniṃ vaiśvānaramupanigacati tata eva tatpakvaṃ śṛtamupahitam bhavati

Here now they say, 'How does that (remainder) of his come to be put on as cooked, as baked?'--In that it is prepared with a sacrificial formula; and, moreover, whatever comes in contact with Agni Vaisvânara even thereby comes to be put on as something cooked, as baked.