Śatapatha Brāhmaṇa ("of a hundred paths") 7.2.2.8

7.2.2.8

sa vā ātmānameva vikṛṣati | na pakṣapucānyātmaṃstadannaṃ dadhāti yadu vā ātmannannaṃ dhīyate tadātmānamavati tatpakṣapucānyatha yatpakṣapuceṣu naiva tadātmānamavati na pakṣapucāni

Only the body (of the altar-site) he ploughs through, not the wings and tail: he thus puts food into the body. And, indeed, the food which is put into the body benefits the body as well as the wings and tail; but that which (is put) into the wings and tail does not benefit either the body or the wings and tail.