Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.2.10

2.4.2.10

taṃ śrapayati | tasminnadhiśrita ājyam pratyānayatyagnau vai devebhyo juhvatyuddharanti manuṣyebhyo 'thaiva pitṝṇāṃ tasmādadhiśrita ājyam pratyānayati

He then boils it. While it stands on the (Dakshina) fire, he pours some clarified butter on it;--for the gods they pour the offering into the fire; for men they take (the food) off the fire; and for the fathers they do in this very manner: hence, they pour the ghee on it while it stands on the fire.