Śatapatha Brāhmaṇa ("of a hundred paths") 6.4.4.1

6.4.4.1

hasta eṣa bhavatyatha paśūnabhimantrayate | etadvā eṣu devāḥ sambhariṣyantaḥ purastādvīryamadadhustathaivaiṣvayametatsambhariṣyanpurastādvīryaṃ dadhāti

That (lump of clay representing Agni) is still in his hand when he addresses the animals; for the gods, being about to equip (Agni), now first laid vigour into them; and in like manner does this (Sacrificer, or priest) now, being about to equip (Agni), first lay vigour into these (cattle).