Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.2.15

3.4.2.15

atha yāstaddevāḥ | juṣṭāstanūḥ priyāṇi dhāmāni sārdhaṃ samavadadire tadindre saṃnyadadhataiṣa vā indro ya eṣa tapati na ha vā eṣo 'gre tatāpa yathā haivaidamanyatkṛṣṇamevaṃ haivāsa tenaivaitadvīryeṇa tapati tasmādyadi bahavo dīkṣerangṛhapataya eva vratamabhyutsicya prayaceyuḥ sa hi teṣāmindrabhājanam bhavati yadyu dakṣiṇāvatā dīkṣeta yajamānāyaiva vratamabhyutsicya prayaceyuridaṃ hyāhurindro yajamāna iti

Now those favourite forms and desirable powers which the gods put together, they then deposited in Indra;--Indra verily is he that burns yonder (the sun); but he indeed did not burn in the beginning, but as now everything else is dark, so was he then; and it is by that very energy (derived from those divine objects) that he burns. Hence, if many persons perform the consecration, let it (the Tânûnaptra butter), after pouring the fast-milk to it, be handed only to the master of the house, since he, among them, is the representative of Indra. And if he perform the consecration by means of an (offering) with a dakshinâ, let them hand it (the butter) to the sacrificer, after pouring the fast-milk to it, for thus it is said,--'The Sacrificer is Indra.'