Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.1.11

4.4.1.11

yadveva vaiśvadevaṃ grahaṃ gṛhṇāti | vaiśvadevaṃ vai tṛtīyasavanaṃ taducyata eva sāmato yasmādvaiśvadevaṃ tṛtīyasavanamucyata ṛkto 'thaitadeva yajuṣṭaḥ puraścaraṇato yadetam mahāvaiśvadevaṃ gṛhṇāti

And again why he draws the Vaisvadeva graha. The evening feast belongs to the All-gods: thus indeed it is called on the part of the Sâman, in that the evening feast is called Vaisvadeva on the part of the Rik, and in the same way on the part of the Yagus, by way of preparatory rite, when he draws that Mahâ-vaisvadeva graha.