Shatapatha Brahmana 10.1.2.2

10.1.2.2

ayaṃ vāva loka eṣo'gniścitaḥ antarikṣam mahāvrataṃ dyaurmahadukthaṃ tasmādetāni sarvāṇi sahopeyādagnim mahāvratam mahadukthaṃ saha hīme lokā asṛjyanta tadyadagniḥ prathamaścīyate'yaṃ hyeṣāṃ lokānām prathamo'sṛjyatetyadhidevatam

This built Fire-altar, doubtless, is this (terrestrial) world, the Great Rite the air, and the Great Litany the sky: all these, the Fire-altar, the Great Rite, and the Great Litany, one ought therefore to undertake together, for these worlds were created together; and as to why the Fire-altar is built first, it is because of these worlds this (terrestrial) one was created first. Thus with regard to the deity.