Śatapatha Brāhmaṇa ("of a hundred paths") 4.5.7.2

4.5.7.2

aṣṭau vasavaḥ | ekādaśa rudrā dvādaśādityā ime eva dyāvāpṛthivī trayastriṃśyau trayastriṃśadvai devāḥ prajāpatiścatustriṃśastadenam prajāpatiṃ karotyetadvā astyetaddhyamṛtaṃ yaddhyamṛtaṃ taddhyastyetadu tadyanmartyaṃ sa eṣa prajāpatiḥ sarvaṃ vai prajāpatistadenam prajāpatiṃ karoti tasmādetāścatustriṃśadvyāhṛtayo bhavanti prāyaścittayo nāma

There are eight Vasus, eleven Rudras, twelve Âdityas; and these two, Heaven and Earth, are the (thirty-second and) thirty-third. And there are thirty-three gods, and Pragâpati is the thirty-fourth;--thus he makes him (the sacrificer, or Yagña) to be Pragâpati: now that is, for that is immortal, and what is immortal that is. But what is mortal that also is Pragâpati; for Pragâpati is everything: thus he makes him to be Pragâpati, and hence there are these thirty-four utterances, called expiations.