Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.8.10

4.6.8.10

atha yadahareṣāṃ dīkṣā samaiti | araṇiṣvevāgnīntsamārohyopasamāyanti yatra dīkṣiṣyamāṇā bhavanti gṛhapatireva prathamo manthate 'thetare paryupaviśya manthante te jātaṃ jātamevānupraharanti gṛhapatergārhapatye gṛhapatereva gārhapatyāduddhṛtyāhavanīyaṃ dīkṣante teṣāṃ samāna āhavanīyo bhavati samāno gārhapatyo dīkṣopasatsu

But if their consecration falls upon the same day, then, taking up the fires (again) on the churning-sticks, they betake themselves to where they intend to perform the consecration-ceremony. The Grihapati churns first, and then the others churn, seated round about him, and throw each the (fire) produced by him on the Grihapati's Gârhapatya. Having taken out the Âhavanîya from the Grihapati's Gârhapatya, they perform the Dîkshâ. Theirs is the same Âhavanîya and the same Gârhapatya during the consecration and the Upasads.