Śatapatha Brāhmaṇa ("of a hundred paths") 1.9.2.35

1.9.2.35

tato devāḥ | sarvaṃ yajñaṃ saṃvṛjyātha yatpāpiṣṭhaṃ yajñasya bhāgadheyamāsīttenainānnirabhajannasnā paśoḥ phalīkaraṇairhaviryajñātsunirbhaktā asannityeṣa vai sunirbhakto yam bhāginaṃ nirbhajantyatha yamabhāgaṃ nirbhajantyaiva sa tāvacaṃsata uta hi vaśo labdhvāha kim mā babhaktheti sa yamevaibhyo devā bhāgamakalpayaṃstamevaibhya eṣa etadbhāgaṃ karotyatha yadadho 'dhaḥ kṛṣṇājinamupāsyatyanagnāvevaibhya etadandhe tamasi praveśayati tatho evāsṛkpaśo rakṣasām bhāgo 'sītyanagnāvandhe tamasi praveśayati tasmātpaśostedanīṃ na kurvanti rakṣasāṃ hi sa bhagaḥ

Thereupon the gods obtained possession of the whole of the sacrifice, and dispossessed those (Asuras) of it by (giving them) what was the worst part of the sacrifice, to wit, with the blood of the victim (they dispossessed them) of the animal sacrifice, and with the refuse of the rice of the haviryagña. 'May they be duly dispossessed of the sacrifice,' they thought for he indeed is duly dispossessed, who is dispossessed even while obtaining a (worthless) share. He, on the other hand, who is dispossessed without any share whatever, hopes for a while, and when it occurs to him, he says, 'What share hast thou given me?' Hence what share the gods set apart for those (Asuras), that same share he now makes over to them in pouring (the refuse of the rice) right under the black antelope skin. He thereby casts it into blind darkness, where there is no (sacrificial) fire. And in the same way he casts the blood of the victim into blind darkness, where there is no fire; thinking, 'Thou art the Rakshas' share!' For this reason they use not the gore of the victim (for sacrificial purposes), since it is the Rakshas' share.