Shatapatha Brahmana 8.5.3

He then lays down the Stomabhâgâ (praise-sharing bricks). For at that time Indra set his mind upon that food of Pragâpati, and tried to go from him. He spake, 'Why dost thou go from me? why dost thou leave me?'--'Give me the essence of that food: enter me therewith!'--'So be it!' so he gave him the essence of that food, and entered him therewith.

Now he who was that Pragâpati is this very Agni (the fire-altar) that is now being built up; and that food is these Khandasyâ (bricks); and that essence of food is these Stomabhâgâs; and he who was Indra is yonder Âditya (the sun): he indeed is the Stoma (hymn of praise), for whatsoever praises they sing, it is him they praise thereby,--it is to that same Stoma he gave a share; and inasmuch as he gave a share (bhâga) to that Stoma, these are (called) Stomabhâgâs.

[He lays them down, with, Vâg. S. XV, 6. 7], 'By the ray quicken thou the truth for truth!'--the ray, doubtless, is that (sun), and ray is food; having put together that (sun) and the essence thereof, he makes it enter his own self;--'by the starting, by the law, quicken the law!'--the starting, doubtless, is that (sun), and the starting also means food: having put together that (sun) and the essence thereof, he makes it enter his own self;--'by the going after, by the sky, quicken the sky!'--the going after, doubtless, is that (sun), and the going after also means food; having put together that (sun) and the essence thereof, he makes it enter his own self. Thus whatever he mentions here, that and the essence thereof he puts together and makes it enter his own self: 'By such and such quicken thou such and such!'--'Such and such thou art: for such and such (I deposit) thee!'--'By the lord, by strength, quicken strength!' thus they (the bricks) are divided into three kinds, for food is of three kinds.

And as to why he lays down the Stomabhâgâs. Now the gods, having laid down the far-shining layer, mounted it. They spake, 'Meditate ye!' whereby, doubtless, they meant to say, 'Seek ye a layer!' Whilst meditating, they saw even the firmament, the heavenly world, and laid it down. Now that same firmament, the heavenly world, indeed is the same as these Stomabhâgâs, and thus in laying down these, he lays down the firmament, the heavenly world.

The first three (bricks) are this (terrestrial) world, the second (three) the air, and the third (three) the sky, the fourth the eastern, the fifth the southern, the sixth the western, and the seventh the northern regions.

These twenty-one bricks, then, are these worlds and the regions, and these worlds and the regions are a foundation, and these worlds and the regions are twenty-one: whence they say, 'the Ekavimsa (twenty-one-fold) is a foundation.'

And the eight bricks which remain over are the Gâyatrî consisting of eight syllables; but the Gâyatrî is the Brahman, and as to that Brahman, it is yonder burning disk: it burns, while firmly-established on that twenty-one-fold one, as on a foundation, whence it does not fall down.

Now some lay down a thirtieth (Stomabhâgâ), with, 'Beautifully arrayed, quicken thou the kshatra for the kshatra!' saying, 'Of thirty syllables is the Virâg (metre) and this layer is virâg (far-shining).' But let him not do so: they (who do so) exceed (this layer so as not to be) amounting to the twenty-one-fold, and to the Gâyatrî; and that undiminished Virâg, doubtless, is the world of Indra: in the world of Indra they raise a spiteful enemy of equal power (to Indra), and thrust Indra out of the world of Indra. And at his own sacrifice the Sacrificer assuredly is Indra: in the Sacrificer's realm they raise for the Sacrificer a spiteful enemy of equal power, and thrust the Sacrificer out of the Sacrificer's own realm. But, surely, that fire which they bring hither is no other than this Sacrificer: by means of his foundation it is he who is the thirtieth (brick) in this (layer).