Śatapatha Brāhmaṇa ("of a hundred paths") 2.1.2.9

2.1.2.9

atha yasmānnā mṛgaśīrṣa ādadhīta | prajāpatervā etacarīraṃ yatra vā enaṃ tadāvedhyaṃstadiṣuṇā trikāṇḍenetyāhuḥ sa etacarīramajahādvāstu vai śarīramayajñiyaṃ nirvīryaṃ tasmānna mṛgaśīrṣa ādadhīta

On the other hand (it is argued) why one should not set up his fire under Mrigasîrsha. The latter, indeed, is Pragâpati's body. Now, when they (the gods) on that occasion pierced him with what is called 'the three-knotted arrow,' he abandoned that body, for the body is a mere relic (or dwelling, vâstu), unholy and sapless. He should therefore not set up his fires under Mrigasîrsha.