Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.1.8

3.8.1.8

tadu tathā na kuryāt | yathā vai grasitamevamasyaitadbhavati yadenena paryagniṃ karoti sa yathā grasitamanuhāyācidya tadanyasmai prayacedevaṃ tattasmādetasyaivolmukasyāṅgārānnimṛdya tasminnenaṃ śrapayeyuḥ

Let him, however, not do this. For in that he carries fire round it, it (the victim) becomes as food swallowed by that (firebrand), and it would be as if he were to seize and tear out food that has been swallowed and offer it to some one else; let them, therefore, crumble some coals off that same firebrand, and thereon cook that (victim).