Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.1.5

5.3.1.5

atha śvo bhūte | sūtasya gṛhānparetya vāruṇaṃ yavamayaṃ caruṃ nirvapati savo vai sūtaḥ savo vai devānāṃ varuṇastasmādvāruṇo bhavatyetadvā asyaikaṃ ratnaṃ yatsūtastasmā evaitena sūyate taṃ svamanapakramiṇaṃ kurute tasyāśvo dakṣiṇā sa hi vāruṇo yadaśvaḥ

And on the following day, he goes to the house of the Sûta (court-minstrel and chronicler), and prepares a barley pap for Varuna; for the Sûta is a spiriter (sava), and Varuna is the spiriter of the gods: therefore it is for Varuna. And he, the Sûta, assuredly is one of his (the king's) jewels: it is for him that he is thereby consecrated; and him he makes his own faithful (follower). The sacrificial fee for this one is a horse, for the horse is Varuna's own.