Shatapatha Brahmana 9.2.1.21

9.2.1.21

yadvevāgnā utsādayati | ime vai lokā eṣo 'gniragnirvāyurādityastadete pravargyāḥ sa yadanyatrāgnerutsādayedetāṃstaddevānbahirdhaibhyo lokebhyo dadhyādatha yadagnā utsādayatyetānevaitaddevāneṣu lokeṣu dadhāti

And, again, as to why he sets it out on the fire-altar;--that fire-altar is these worlds, and those Pravargya (vessels) are Agni (fire), Vâyu (wind), and Âditya (sun): hence, were he to set them out in any other place than the fire-altar, he would place those gods outside these worlds; but in that he sets them out on the fire-altar, he places those gods in these worlds.