Śatapatha Brāhmaṇa ("of a hundred paths") 1.5.2.14

1.5.2.14

sa hotā nāpavyāharet | ā vaṣaṭkārāttaṃ vaṣaṭkāreṇāgnāveva yonau reto bhūtaṃ siñcatyagnirvai yoniryajñasya sa tataḥ prajāyate

The Hotri must utter nothing improper until the vashat-call. With the vashat-call he pours it (the sacrifice) into the fire, as seed into the womb; for the fire is indeed the womb of the sacrifice, since from thence it is brought forth.