Śatapatha Brāhmaṇa ("of a hundred paths") 3.5.3.5

3.5.3.5

udaramevāsya sadaḥ | tasmātsadasi bhakṣayanti yaddhīdaṃ kiṃ cāśnantyudara evedaṃ sarvaṃ pratitiṣṭhatyatha yadasminviśve devā asīdaṃstasmātsado nāma ta u evāsminnete brāhmaṇā viśvagotrāḥ sīdanti

The Sadas (tent for the priests) is no other than his belly: wherefore they feed in the Sadas, for whatever food is eaten here on earth all that settles down here in the belly. And because all the gods sat (sad) in it therefore it is called Sadas: and so do these Brahmans of every family now sit therein.