Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.1.12

6.2.1.12

ta ete sarve paśavo yadagniḥ | tasmādagnau paśavo ramante p!sminnagnirādhīyate 'gnirhyeṣa yatpaśavastato vai prajāpataśubhireva tatpaśavo ramante tasmādyasya paśavo bhavanti tairagnirabhavat etairatra sarvaiḥ prajāpatirayakṣyata tadevāgnerantam par

And because Agni is all those animal victims, therefore animals delight (being) near the fire,-- there animals sport with animals. Hence the (sacrificial) fire is set up with him who possesses cattle; for inasmuch as Agni (was) the same as cattle, therefore Pragâpati (the lord of creatures or generation) became Agni.