Shatapatha Brahmana 10.5.1

The mystic import of this Fire-altar, doubtless, is Speech; for it is with speech that it is built: with the Rik, the Yagus and the Sâman as the divine (speech); and when he (the Adhvaryu) speaks with human speech, 'Do ye this! do ye that!' then also it (the altar) is built therewith.

Now, this speech is threefold--the Rik-verses, the Yagus-formulas, and the Sâman-tunes;--thereby the Fire-altar is threefold, inasmuch as it is built with that triad. Even thus, then, it is threefold; but in this respect also it is threefold, inasmuch as three kinds of bricks are put into it--those with masculine names, those with feminine names, and those with neuter names; and these limbs of men also are of three kinds--those with masculine names, those with feminine names, and those with neuter names.

This body (of the altar), indeed, is threefold; and with this threefold body he obtains the threefold divine Amrita (nectar, immortality). Now all these (bricks) are called 'ishtakâ (f.),' not 'ishtakah (m.),' nor 'ishtakam (n.):' thus (they are called) after the form of speech (vâk, f.), for everything here is speech--whether feminine (female), masculine (male), or neuter--for by speech everything here is obtained. Therefore he 'settles' all (the bricks) with, 'Aṅgiras-like lie thou steady (dhruvâ, f.)!' not with, 'Aṅgiras-like lie thou steady (dhruvah, m.)!' or with, 'Aṅgiras-like lie thou steady (dhruvam, n.)!' for it is that Speech he is constructing.

Now, this speech is yonder sun, and this (Agni, the Fire-altar) is Death: hence whatsoever is on this side of the sun all that is field by Death; and he who builds it (the Fire-altar) on this side thereof, builds it as one held by Death, and he surrenders his own self unto Death; but he who builds it thereabove, conquers recurring Death, for by his knowledge that (altar) of his is built thereabove.

This speech, indeed, is threefold--the Rik-verses, the Yagus-formulas, and the Sâman-tunes the Rik-verses are the orb, the Sâman-tunes the light, and the Yagus-formulas the man (in the sun); and that immortal element, the shining light, is this lotus-leaf: thus, when he builds up the Fire-altar after laying down the lotus-leaf, it is on that immortal element that he builds for himself a body consisting of the Rik, the Yagus, and the Sâman; and he becomes immortal.