Śatapatha Brāhmaṇa ("of a hundred paths") 6.6.4.13

6.6.4.13

atha yadi gārhapatyo 'nugacet | araṇī vāva sa gacatyaraṇibhyāṃ hi sa āhṛto bhavatyaraṇibhyāmevainam mathitvopasamādhāya prāyaścittī karoti

And if the Gârhapatya fire were to go out, it is doubtless to the churning-sticks that it goes, for from the churning-sticks it has been taken. Having churned it out with the churning-sticks, and put fuel on it, he performs two expiations.