Śatapatha Brāhmaṇa ("of a hundred paths") 4.3.4.1

4.3.4.1

ghnanti vā etadyajñam | yadenaṃ tanvate yannveva rājānamabhiṣuṇvanti tattaṃ ghnanti yatpaśuṃ saṃjñapayanti viśāsati tattaṃ ghnantyulūkhalamusalābhyāṃ dṛṣadupalābhyāṃ haviryajñaṃ ghnanti

Now, they slay the sacrifice, when they spread (perform) it:--to wit, when they press out the king (Soma), they slay him; when they quiet the victim, they slay it; and with mortar and pestle, with the upper and nether millstone, they slay the havis offering.