Śatapatha Brāhmaṇa ("of a hundred paths") 1.4.5.12

1.4.5.12

sā ha vākparoktā visiṣmiye | tasyai garbhaḥ papāta sā ha vākprajāpatimuvācāhavyavāḍevāhaṃ tubhyam bhūyāsaṃ yāṃ mā parāvoca iti tasmādyatkiṃ ca prājāpatyaṃ yajñe kriyata upāṃśveva tatkriyate havyavāḍhi vākprajāpataya āsīt

Then Speech (vâk, fem.) being thus gainsaid, was dismayed and miscarried. She, Speech, then said to Pragâpati, 'May I never be thy oblation-bearer, I whom thou hast gainsaid!' Hence whatever at the sacrifice is performed for Pragâpati, that is performed in a low voice; for speech would not act as oblation-bearer for Pragâpati.