Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.9.9

4.6.9.9

atha dvitīyāṃ juhīti | upasṛjandharuṇam mātra ityagnimevaitatpṛthivyā upasṛjannāha dharuṇo mātaraṃ dhayannityagnimevaitatpṛthivīṃ dhayantamāha rāyaspoṣamasmāsu dīdharatsvāheti paśavo vai rāyaspoṣaḥ paśūnevaitadātmanniyacante

And the second he offers with, 'Letting the sucking calf to the mother,'--he means to say by this, 'letting the fire go to the earth;'--'a sucking calf drinking from the mother,'--he thereby means the fire sucking the (moisture of the) earth;--'may he maintain increase of wealth among us,--Hail!' increase of wealth is cattle: they thus secure cattle for themselves.