Shatapatha Brahmana 5.1.2.13

5.1.2.13

ta ubhaye catustriṃśadgrahāḥ sampadyante | trayastriṃśadvai devāḥ prajāpatiścatustriṃśastatprajāpatimujjayati

These two amount to thirty-four cups; for there are thirty-three gods, and Pragâpati is the thirty-fourth: he thus wins Pragâpati.