Śatapatha Brāhmaṇa ("of a hundred paths") 13.2.2.14

13.2.2.14

tānkathamāprīṇīyādityāhuḥ samiddho añjankṛdaram matīnāmiti bārhadukthībhirāprīṇīyādbṛhaduktho ha vai vāmadevyo'śvo vā sāmudriraśvasyāprīrdadarśa tā etāstābhirevainametadāprīṇīma iti vadanto na tathā kuryājjāmadagnībhirevāprīṇīyātprajāpatirvai jamadagniḥ so'śvamedhaḥ svayaivainaṃ devatayā samardhayati tasmājjāmadagnībhirevāprīṇīyāt

'How is he to appease these?' they ask. 'Let him appease them with the Bârhaduktha verses, "Enkindled, anointing the lap of the faithful(f.)...;" for Brihaduktha, the son of Vâmadeva, or Asva, son of Samudra, saw these very (verses) to be the âprî-verses of the horse: it is by means of these we appease it,' so they say. But let him not do so; let him appease it with the Gâmadagna verses; for Gamadagni is Pragâpati, and so is the Asvamedha: he thus supplies it with its own deity; let him therefore appease (the victims) with the Gâmadagna verses.