Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.3.1

3.8.3.1

yaddevatyaḥ paśurbhavati | taddevatyam puroḍāśamanunirvapati tadyatpuroḍāśamanunirvapati sarveṣāṃ vā eṣa paśūnām medho yadvrīhiyavau tenaivainametanmedhena samardhayati kṛtsnaṃ karoti tasmātpuroḍāśamanunirvapati

For the same deity for which there is a victim, he subsequently prepares a sacrificial cake. The reason why he subsequently prepares a cake is this. Rice and barley, truly, are the sacrificial essence of all animals (victims); with that same essence he now completes that (victim) and makes it whole. This is why he subsequently prepares a sacrificial cake.