Śatapatha Brāhmaṇa ("of a hundred paths") 5.5.5

He prepares a cake on twelve potsherds for Indra and Vishnu. Now as to why he makes this offering. Of old, everything here was within Vritra, to wit, the Rik, the Yagus, and the Sâman. Indra wished to hurl the thunderbolt at him.

He said to Vishnu, 'I will hurl the thunderbolt at Vritra, stand thou by me!'--'So be it!' said Vishnu, 'I will stand by thee: hurl it!' Indra aimed the thunderbolt at him. Vritra was afraid of the raised thunderbolt.

He said, 'There is here a (source of) strength: I will give that up to thee; but do not smite me!' and gave up to him the Yagus-formulas. He (Indra) aimed at him a second time.

He said, 'There is here a (source of) strength: I will give that up to thee; but do not smite me!' and gave up to him the Rik-verses. He aimed at him a third time.

'There is here a (source of) strength: I will give that up to thee; but do not smite me!' and gave up to him the Sâman-hymns (or tunes). Therefore they spread the sacrifice even to this day in the same way with those (three) Vedas, first with the Yagus-formulas, then with the Rik-verses, and then with the Sâman-hymns; for thus he (Vritra) at that time gave them up to him.

And that which had been his (Vritra's) seat, his retreat, that he shattered, grasping it and tearing it out: it became this offering. And because the science (the Veda) that lay in that retreat was, as it were, a threefold (tridhâtu) one, therefore this is called the Traidhâtavî (ishti).

And as to why the oblation is one for Indra and Vishnu, it is because Indra raised the thunderbolt, and Vishnu stood by him.

And why it is (a cake) on twelve potsherds,--there are twelve months in the year, and the offering is of equal measure with the year: therefore it is one of twelve potsherds.

He prepares it of both rice and barley. He first puts on (the fire) a ball of rice, that being a form (symbol) of the Yagus-formulas; then one of barley, that being a form of the Rik-verses; then one of rice, that being a form of the Sâman-hymns. Thus this is made to be a form of the triple science: and this same (offering) becomes the Udavasânîyâ-ishti (completing oblation) for the performer of the Râgasûya.

For, verily, he who performs the Râgasûya gains for himself (the benefit of) all sacrificial rites, all offerings, even the spoonful-oblations; for him the sacrifice becomes as it were exhausted, and he, as it were, turns away from it. Now the whole sacrifice is just as great as that triple Veda; and this (offering) now is made a form of that (Veda, or sacrifice); this is its womb, its seat: thus he commences once more the sacrifice by means of that triple Veda; and thus his sacrifice is not exhausted, and he does not turn away from it.

And, verily, he who performs the Râgasûya gains for himself all sacrificial rites, all offerings, even the spoonful-oblations; and this offering, the Traidhâtavî (ishti), is instituted by the gods: 'May this offering also be performed by me, may I be consecrated by this one also!' thus he thinks, and therefore this is the completing offering for him who performs the Râgasûya.

And also for him who would give (to the priests) a thousand (cows) or more, let this be the completing offering. For he who gives a thousand or more becomes as it were emptied out; and that triple Veda is the thousandfold progeny of Vâk (speech): him who was emptied out he thus fills up again with a thousand; and therefore let it be for him also the completing offering.

And also for those who would sit through (perform) a long sacrificial session, for a year or more, let this be the completing offering. For by those who sit through a long sacrificial session, for a year or more, everything is obtained, everything conquered; but this (offering) is everything: let it therefore be for them also the completing offering.

And indeed one may also practise magic by this (offering); for it was thereby that Ârani bewitched Bhadrasena Âgâtasatrava: 'Quick, then, spread (the barhis)!' thus Yâgñavalkya used to say. And by this (offering) indeed Indra also shattered Vritra's retreat; and, verily, he who therewith practises magic shatters thereby the retreat (of his enemy): therefore one may also practise magic with this (offering).

And, indeed, one may also heal thereby; for, verily, whomsoever one would heal by a single rik, by a single yagus, by a single sâman, him he would indeed render free from disease; how much more so by the triple Veda! Therefore one may also heal by this (offering).

Three gold pieces of a hundred mânas each are the sacrificial fee for this (offering). He presents them to the Brahman; for the Brahman neither performs (like the Adhvaryu), nor chants (like the Udgâtri), nor recites (like the Hotri), and yet he is an object of respect. And with gold they do nothing, and yet it is an object of respect: therefore he presents to the Brahman three gold pieces of a hundred mânas each.

Three milch cows (he gives) to the Hotri;--for three milch cows mean abundance, and the Hotri means abundance: therefore (he gives) three milch cows to the Hotri.

Three garments (he gives) to the Adhvaryu;--for the Adhvaryu 'spreads' the sacrifice, and the garments spread themselves (over the body): therefore (he gives) three garments to the Adhvaryu. A bullock (he gives) to the Agnîdh.

Now there are here either twelve, or thirteen gifts, and there are either twelve or thirteen months in the year;--the offering thus is of equal measure with the year: that is why there are either twelve or thirteen sacrificial gifts.