Śatapatha Brāhmaṇa ("of a hundred paths") 3.9.3.10

3.9.3.10

atha yatsamidhamabhyādadhāti | candāṃsyevaitatsaminddhe 'tha yaddhotā prātaranuvākamanvāha candāṃsyevaitatpunarāpyāyayatyayātayāmāni karoti yātayāmāni vai devaiścandāṃsi candobhirhi devāḥ svargaṃ lokaṃ samāśnuvata na vā atra stuvate na śaṃsanti taccandāṃsyevaitatpunarāpyāyayatyayātayāmāni karoti tairayātayāmairyajñaṃ tanvate tasmāddhotā prātaranuvākamanvāha

And when he puts on a kindling-stick, it is the metres he thereby kindles. And when the Hotri recites the morning-prayer, he thereby again strengthens the metres, makes them to be of unimpaired vigour; for the metres had their vigour impaired by the gods, since it was through the metres that the gods reached the heavenly worlds; they neither sing praises (chants) nor recite (sastras) here. Hereby he now again strengthens the metres and makes them to be of unimpaired vigour; and by means of them, thus unimpaired in vigour, they perform the sacrifice; this is why the Hotri recites the morning-prayer.