Śatapatha Brāhmaṇa ("of a hundred paths") 13.4.4.4

13.4.4.4

prajāpatinā sutyāsu evamevāharahaḥ parihṛtāsveva vasatīvarīṣūdavasānīyāyāmantataḥ saṃsthitāyāṃ tadyadenam prajāpatinā saṃgāyanti prajāpatinaivainam tadantataḥ salokaṃ kurvanti

On the Sutyâ-days (they sing of him) along with Pragâpati in the same way day by day, after the Vasatîvarî (water) has been carried round, and the Udavasânîyâ (offering) has been finally completed. The reason why they thus sing of him along with Pragâpati is that they thereby finally make him share the same world with Pragâpati.