Shatapatha Brahmana 14.3.1.33

14.3.1.33

atha yaiṣā gharmadughā tāmadhvaryave dadāti tapta-iva vai gharmastaptamivādhvaryurniṣkrāmati tasmāttāmadhvarya ve dadāti

And that cow which yielded the Gharma-milk he gives to the Adhvaryu; for scorched, as it were, is the Gharma, and the Adhvaryu comes forth (from the sacrificial ground) like something scorched: therefore he gives it to the Adhvaryu.