Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.3.20

3.8.3.20

atha vasāhomaṃ gṛhṇāti | reḍasīti lelayeva hi yūstasmādāha reḍasītyagniṣṭvā śrīṇātvityagnirhyetacrapayati tasmādāhāgniṣṭvā śrīṇātvityāpastvā samariṇannityāpo hyetamaṅgebhyo rasaṃ sambharanti tasmādāhāpastvā mamariṇanniti

He then takes the oblation of gravy with (Vâg. S. VI, 18), 'Thou art trembling,' for quivering, as it were, is the broth: hence he says, 'Thou art trembling;'--'May Agni prepare thee!' for the fire does indeed cook it: hence he says, 'May Agni prepare thee!'--'The waters have washed thee together,' for the water indeed gathers together that (fat) juice from the limbs: hence he says, 'The waters have washed thee together.'