Śatapatha Brāhmaṇa ("of a hundred paths") 6.1.2.21

6.1.2.21

atho āhuḥ | prajāpatireva visrasto devānabravītsam mā dhatteti te devā agnimabruvaṃstvayīmam pitaram prajāpatim bhiṣajyāmeti sa vā ahametasmintsarvasminneva viśānīti tatheti tasmādetam prajāpatiṃ santamagnirityācakṣate

But they say,--Pragâpati, when relaxed, said to the gods, 'Restore me!' The gods said to Agni, 'In thee we will heal this our father Pragâpati.'-- 'Then I will enter into him, when whole,' he said.--'So be it!' they said. Hence, while being Pragâpati, they yet call him Agni.