Shatapatha Brahmana 11.7.4.2

11.7.4.2

tadāhuḥ yajedājyabhāgau nā3 iti yajedityāhuścakṣuṣī vā ete yajñasya yadājyabhāgau kimṛte puruṣaścakṣurbhyāṃ syāditi yāvadvai bhāginaṃ svena bhāgadheyena na nirbhajantyanirbhakto vai sa tāvanmanyate'tha yadaiva taṃ svena bhāgadheyena nirbhajantyathaiva sa nirbhakto manyate sa yatraitaddhotānvāhāsnā rakṣaḥ saṃsṛjatāditi tadenaṃ svena bhāgadheyena nirbhajati

As to this they say, 'Should he offer the butter-portions or not?'--'Let him offer them,' they say; 'for the two butter-portions are the eyes of the sacrifice, and what were man without eyes?' For as long as a co-sharer is not bought off by (receiving) a share of his own, so long does he consider himself not bought off; but when he is bought off by a share of his own, then, indeed, he considers himself bought off: when the Hotri, on that occasion, recites, 'Endow the Rakshas with blood!' he buys him off by (assigning to him) a share of his own.