Śatapatha Brāhmaṇa ("of a hundred paths") 6.1.2.33

6.1.2.33

atho eka iti brūyāt | aviritīyaṃ vā aviriyaṃ hīmāḥ sarvāḥ prajā avatīyamu vā agnirasyai hi sarvo 'gniścīyate tasmādeka iti brūyāt

Or, 'One,' he may say; 'a ewe;' for a ewe (avi) is this earth, since she favours (av) all these creatures. And the fire (altar) also is this earth, for the whole fire (altar) is built up thereof: hence he may say, 'One.'