Shatapatha Brahmana 11.5.5.10

11.5.5.10

te hocuḥ kathaṃ nu bhagavaḥ śastaṃ kathamapratiśastamiti sa hovāca yatra hotāśvinaṃ śaṃsannāgneyāsya kratorgāyatrasya candasaḥ pāraṃ gacāttatpratiprasthātā vasatīvarīḥ parihṛtya maitrāvaruṇasya havirdhānayoḥ prātaranuvākamupākurutāduccairhotā śaṃsati śanairitaro jañjapyamāna ivānvāha tanna vācā vācam pratyeti na candasā candaḥ

They spake, 'How, then, reverend sir, is (the Âsvina-sastra properly) recited and how is the recitation not disturbed?' He spake, 'When the Hotri, in reciting the Âsvina-sastra, reaches the end of the Gâyatra metre of the Âgneya-kratu, the Pratiprasthâtri should carry round the Vasatîvarî water, and bespeak the Prâtar-anuvâka for the Maitrâvaruna (seated) between the two Havirdhâna (carts containing the offering-material). The Hotri recites (the Âsvina-sastra) in a loud voice, and the other (the Maitrâvaruna) repeats (the morning-litany) in a low voice, only just muttering it: in this way he does not run counter to (the Hotri's) speech by (his own) speech, nor metre by metre.