Matsyapurana 167.6

167.6

ye ca yajñakarā viprā ye cartvija iti smṛtāḥ
asmādeva purā bhūtā yajñebhyaḥ śrūyatāṃ tathā //

The Ṛitwika Brâhmaṇas who perform and direct the performance of the sacrifices were first born of Viṣṇu He created Brahmâ first from His mouth, and then from His arms He created Udgâtâ Samaga, Hotâ, and Adhvaryu (the sacrificial priests) From His back came Mitrâvaruṇa Brahmanâchhamsi, Prastotâ, and Prati Prastotâ The Pratīhartâ and the Potâ Brâhmaṇas were produced from the stomach, Achâvakas and Neṣṭas were born from his thighs, Agnidbra Brâhmaṇas from His hands, Subrahmanya Brâhmaṇas from His knees, the Unnetâ and Jâtusa Brâhmaṇas were born from His feet Thus the Lord created sixteen excellent priests who performed the functions of all the sacrifices. Lord Viṣṇu, the very incarnation of the Vedas, rests in sacrifices. The Vedas along with the six aṅgas which dictate karmas are also this Supreme Puruṣa and nothing else—6-12