Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.1.18

2.6.1.18

te sarva eva yajñopavītino bhūtvā | itthādyajamānaśca brahmā ca paścātparītaḥ purastādagnīt

All of them having now become 'sacrificially-invested,' the Sacrificer and Brahman (being) thus (invested) walk round (from the east, along the south) to the west side; and the Âgnîdhra (from the west) to the east side (of the fire).