Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.3.27

1.6.3.27

tadāhuḥ | kimidaṃ jāmi kriyate 'gnīṣomayorevājyasyāgnīṣomayoḥ puroḍāśasya yadanantarhitaṃ tena jāmītyanena ha tvevājāmyājyasyetaram puroḍāśasyetaraṃ tadanyadivetaramanyadivetaram bhavatyṛcamanūcya juṣāṇena yajatyṛcamanūcyarcā yajati tadanyadivetaramanyadivetaram bhavatyanena ha tvevājāmyupāṃśvājyasya yajatyuccaiḥ puroḍāśasya sa yadupāṃśu tatprājāpatyaṃ rūpaṃ tasmāttasyānuṣṭubhamanuvākyāmanvāha vāgghyanuṣṭubvāgghi prajāpatiḥ

On this point it has also been remarked: 'Why this sameness (of performance)? By what is introduced between the butter(-offering) to Agni and Soma and the rice-cake to Agni and Soma, a repetition of performance (is committed).' Sameness (of performance), nevertheless, is avoided in this way: the one (viz. the low-voiced offering) consists of butter, and the other of a rice-cake, hence the one is different from the other. Moreover, after reciting a Rik-verse as anuvâkyâ, he pronounces the yâgyâ with the word 'pleased' (in the case of the butter-portions to Agni and Soma); and after reciting a Rik-verse as anuvâkyâ, he pronounces the yâgyâ in the form of a Rik-verse (in the case of the low-voiced offering to Agni and Soma), hence the one is (again) different from the other. Sameness of performance is also avoided in this way: in a low voice (he utters the formulas when) he offers of the butter, and with a loud voice of the cake; and what is (uttered) in a low voice, that is the manner of Pragâpati: hence he recites for that (low-voiced offering) an anushtubh-verse as the invitatory formula (anuvâkyâ), for the anushtubh represents speech, and Pragâpati also is speech.