Shatapatha Brahmana 8.5.3.8

8.5.3.8

taddhaike | veṣaśrīḥ kṣatrāya kṣatraṃ jinveti triṃśattamīmupadadhati triṃśadakṣarā virāḍvirāḍeṣā citiriti na tathā kuryādati te recayantyekaviṃśasampadamatho gāyatrīsampadamatho indraloko haiṣa yaiṣānyūnā virāḍindrāya ha ta indraloke dviṣantam bhrātṛvyam pratyudyāminaṃ kurvantīndramindralokānnudante yajamāno vai sve yajña indro yajamānāya ha te yajamānaloke dviṣantam bhrātṛvyam pratyudyāminaṃ kurvanti yajamānaṃ yajamānalokānnudante yaṃ vā etamagnimāharantyeṣa eva yajamāna āyatanenaiṣa u evātra triṃśattamī

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).