Shatapatha Brahmana 10.1.4.2

10.1.4.2

sa prathamāṃ citiṃ cinoti sā hāsyaiṣā prāṇa eva tadvai tadamṛtamṛtaṃ hi prāṇaḥ saiṣāmṛtacitiratha purīṣaṃ nivapati taddhāsyaitanmajjaiva tadvai tanmartyam martyo hi majjā tadetasminnamṛte pratiṣṭhāpayati tenāsyaitadamṛtam bhavati

He lays down the first layer,--this, doubtless, is his out- (and in-) breathing, and it is an immortal (element), for the out-breathing is something immortal: this, then, is an immortal layer. He then scatters loose soil thereon,--this, doubtless, is his marrow, and it is a mortal (element), for the marrow is mortal: he establishes it on that immortal (element), and thereby this part of him becomes immortal.