Śatapatha Brāhmaṇa ("of a hundred paths") 5.1.3.7

5.1.3.7

atha saptadaśa prājāpatyānpaśūnālabhate | te vai sarve tūparā bhavanti sarve śyāmāḥ sarve muṣkarāḥ prajāpatiṃ vā eṣa ujjayati yo vājapeyena yajate 'nnaṃ vai prajāpatiḥ paśurvā annaṃ tatprajāpatimujjayati somo vai prajāpatiḥ paśurvai pratyakṣaṃ somastatpratyakṣam prajāpatimujjayati saptadaśa bhavanti saptadaśo vai prajāpatistatprajāpatimujjayati

He then seizes seventeen victims for Pragâpati. They are all hornless, all dark-grey, all (uncastrated) males; for he who offers the Vâgapeya, wins Pragâpati; but Pragâpati is food, and the victim (cattle) is food: he thus wins Pragâpati. And Pragâpati is Soma, and the victim is the visible Soma: he thus wins the visible Pragâpati. There are seventeen (victims), because Pragâpati is seventeenfold: he thus wins Pragâpati.