Śatapatha Brāhmaṇa ("of a hundred paths") 1.2.3.9

1.2.3.9

sa yam puruṣamālabhanta | sa kimpuruṣo 'bhavadyāvaśvaṃ ca gāṃ ca tau gauraśca gavayaścābhavatāṃ yamavimālabhanta sa uṣṭro 'bhavadyamajamālabhanta sa śarabho 'bhavattasmādeteṣām paśūnāṃ nāśitavyamapakrāntamedhā haite paśavaḥ

The man (purusha) whom they had offered up became a mock-man (kim-purusha). Those two, the horse and the ox, which they had sacrificed, became a bos gaurus and a gayal (bos gavaeus) respectively. The sheep which they had sacrificed, became a camel. The goat which they had sacrificed, became a sarabha. For this reason one should not eat (the flesh) of these animals, for these animals are deprived of the sacrificial essence (are impure).