Shatapatha Brahmana 11.1.8.3

11.1.8.3

sa devebhya ātmānam pradāya athaitamātmanaḥ pratimāmasṛjata yadyajñaṃ tasmādāhuḥ prajāpatiryajña ityātmano hyetam pratimāmasṛjata

Having given himself up to the gods, he created that counterpart of himself, to wit, the sacrifice: whence people say, 'The sacrifice is Pragâpati;' for he created it as a counterpart of himself.