Śatapatha Brāhmaṇa ("of a hundred paths") 5.1.5.4

5.1.5.4

atha yadi rājanyo yajate | devasyāhaṃ savituḥ save satyaprasavasa indrasyottamaṃ nākamaruhamiti kṣatraṃ hīndraḥ kṣatraṃ rājanyaḥ

Thrice he sings the Sâman. Having thrice sung it, he descends with, 'At the impulse of the divine Savitri, of true impulsion, I have ascended unto the highest heaven of Brihaspati!'--thus, if a Brâhmana sacrifices, for Brihaspati is the Brahman, and the Brâhmana is the Brahman.