Shatapatha Brahmana 11.6.3.5

11.6.3.5

sa hovāca mahimāna evaiṣāmete trayastriṃśattveva devā iti katame te trayastriṃśadityaṣṭau vasava ekādaśa rudrā dvādaśādityāsta ekatriṃśadindraścaiva prajāpatiśca trayastrṃśāviti

He replied, 'These are their powers, but thirty-three gods indeed there are.'--'Who are those thirty-three? Eight Vasus, eleven Rudras, and twelve Âdityas,--that makes thirty-one; and Indra and Pragâpati make up the thirty-three.'