Shatapatha Brahmana 14.3.1.34

14.3.1.34

atha yaiṣā yajamānasya vratadughā tāṃ hotre dadāti yajño vai hotā yajño yajamānastasmāttāṃ hotre dadāti

And that cow which yielded the Sacrificer's fast-milk he gives to the Hotri; for the Hotri is the sacrifice, and the Sacrificer also is the sacrifice: therefore he gives it to the Hotri.