Shatapatha Brahmana 10.4.2.30

10.4.2.30

tadyatpariśritamupadhatte tadrātrimupadhatte tadanu pañcadaśa muhūrtānmuhūrtānanu pañcadaśāśītīratha yadyajuṣmatīmupadhatte tadaharupadhatte tadanu pañcadaśa mūhūrtānmuhūrtānanu pañcadaśāśītīrevametāṃ trayīṃ vidyāmātmannāvapata ātmankurute so'traiva sarveṣām bhūtānāmātmā bhavati candomaya stomamayaḥ prāṇamayo devatāmayaḥ sa etanmaya eva bhūtvordhva utkrāmati

And whenever he lays down an enclosing-stone, he lays down a night, and along with that fifteen muhûrtas, and along with the muhûrtas fifteen eighties (of syllables). And whenever he lays down a Yagushmatî (brick), he lays down a day, and along with that fifteen muhûrtas, and along with the muhûrtas fifteen eighties (of syllables of the sacred texts). In this manner he puts this threefold lore into his own self, and makes it his own; and in this very (performance) he becomes the body of all existing things, (a body) composed of the metres, stomas, vital airs, and deities; and having become composed of all that, he ascends upwards.