Śatapatha Brāhmaṇa ("of a hundred paths") 7.5.2.14

7.5.2.14

athainānupadadhāti | puruṣam prathamam puruṣaṃ tadvīryeṇāptvā dadhāti madhye puruṣamabhita itarānpaśūnpuruṣaṃ tatpaśūnām madhyato 'ttāraṃ dadhāti tasmātpuruṣa eva paśūnām madhyato 'ttā

He then puts them (the heads) in (the fire-pan), first (that of) the man--having taken possession of the man by strength he sets him up;--the man in the middle; on both sides the other victims: he thus sets the man, as the eater, in the midst of cattle; whence man is the eater in the midst of cattle.