Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.2.14

3.8.2.14

sa yatrācyati | yata etallohitamutpatati tadubhayato 'nakti rakṣasām bhāgo 'sīti rakṣasāṃ hyeṣa bhāgo yadasṛk

And where he skins (the victim), and whence the blood spirts out, there he smears it (the bottom part with blood) on both ends with (Vâg. S. VI, I6), 'Thou art the Rakshas' share!' for that blood is indeed the Rakshas' share.