The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c9.s2.t2.1

c9.s2.t2.1

As in the sacrifice the offerings are thrown into the fire to come forth from it again in a spiritualised form, so too the fire, wherein the corpse is burnt, is a sacrificial fire, through which man passes to come forth out of it again "in a luminous form" (Bṛih.). This conception of the rising from the body as an offering, is also applied by the section under discussion to the descent of the soul into the body from the Beyond: this descent is a passing through five transformations, which are spoken of as five successive sacrificial acts and are described in detail.