Śatapatha Brāhmaṇa ("of a hundred paths") 5.2.5.7

5.2.5.7

atha yadaindrāpauṣṇaḥ | carurbhavatīndro vai yajamānaḥ pauṣṇāḥ paśavaḥ sa yānevāsmā agnirdātā paśūndadāti tairevaitatsaṃspṛśate tānātmankurute

And as to why there is a pap for Indra and Pûshan;--Indra is the Sacrificer, and the cattle are Pûshan's: whatever cattle Agni, the giver, gives him, therewith he now puts himself in contact, those he makes his own.