Shatapatha Brahmana 10.1.4.6

10.1.4.6

pañcamīṃ citiṃ cinoti sā hāsyaiṣā samāna eva tadvai tadamṛtamamṛtaṃ hi samānaḥ saiṣāmṛtacitistadetanmartyamubhayato'mṛtena parigṛhṇāti tenāsyaitadamṛtam bhavatyatha purīṣaṃ nivapati taddhāsyaitanmeda eva tadvai tanmartyam martyaṃ hi medastadetasminnamṛte pratiṣṭhāpayati tenāsyaitadamṛtam bhavati

He lays down the fifth layer,--this, doubtless, is his central (or pervading) breathing, and it is an immortal (element), for the central breathing is something immortal: this, then, is an immortal layer. He thus encompasses that mortal (element) on both sides by an immortal one, and thereby that part of him becomes immortal. He then scatters loose soil thereon,--this, doubtless, is his fat, and it is a mortal (element), for the fat is mortal: he establishes it on that immortal (element), and thereby this part of him becomes immortal.