Shatapatha Brahmana 11.1.2.1

11.1.2.1

ghnanti vā etadyajñam yadenaṃ tanvate yannveva rājānamabhiṣuṇvani[ tattaṃ ghnanti yatpaśuṃ saṃjñapayanti viśāsati tattaṃ ghnantyulūkhalamusalābhyāṃ dṛṣadupalābhyāṃ haviryajñaṃ ghnanti

Now when they spread (and perform) the sacrifice, they kill it; and when they press out king Soma, they kill him; and when they 'quiet' and cut up the victim, they kill it,--it is by means of the mortar and pestle, and by the two mill-stones that they kill the Haviryagña (grain-offering).