Śatapatha Brāhmaṇa ("of a hundred paths") 4.5.2.7

4.5.2.7

tāni paśuśrapaṇe śrapayanti | tadevaitam medhaṃ śrapayantyuṣṇīṣeṇāveṣṭya garbham pārśvataḥ paśuśrapaṇasyopanidadhāti yadā śṛto bhavatyatha samudyāvadānānyevābhijuhoti naitam medhamudvāsayanti paśuṃ tadevaitam medhamudvāsayanti

They cook them on the cooking-fire of the animal offering: at the same time they cook that fat juice. Having wrapped the embryo in the cloth, he lays it down by the side of the cooking-fire. When it (the victim) is cooked, he puts together the (flesh) portions and bastes only them, but not that juice. They remove the victim (from the fire); and at the same time they remove that juice.