Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.4.17

8.2.4.17

sa eṣa paśuryadagniḥ | so 'traiva sarvaḥ kṛtsnaḥ saṃskṛtastasya yāḥ purastādupadadhāti śiro 'sya tā atha yā dakṣiṇataścottarataśca sa ātmātha yāḥ paścāttatpucam

Now that animal is the same as Agni: (as such) he is even now made up whole and entire. Those (bricks) which he places in front are his head; those on the right and left sides are his body, and those behind his tail.