Śatapatha Brāhmaṇa ("of a hundred paths") 9.3.4.12

9.3.4.12

āhavanīya u haike 'bhiṣiñcati | svargo vai loka āhavanīyastadenaṃ svarge loke 'bhiṣiñcāma iti na tathā kuryāddaivo vā asyaiṣa ātmā mānuṣo 'yamanena hāsya te martyenātmanaitaṃ daivamātmanaitaṃ daivamānamanuprasajanti yaṃ tathābhiṣiñcanti

And some, indeed, anoint him on the Âhavanîya, on the ground that the Âhavanîya is the world of heaven, and that they thus anoint him in the world of heaven. But let him not do so, for that (Âhavanîya, the fire-altar,) is his (the Sacrificer's) divine body, and this (Sacrificer, or Sacrificer's real body) is his human one: they thus attach that divine body of his to this his mortal body, if they anoint him in this way.