Shatapatha Brahmana 10.5.4.3

10.5.4.3

dyaurha tvevaiṣo'gniścitaḥ tasyāpa eva pariśrito yathā ha vā idaṃ kośaḥ samubjita evamime lokā apsvantastadyā imāṃlokānpareṇāpastāḥ pariśrito devā yajuṣmatya iṣṭakā yadevaitasmiṃloke'nnaṃ tatsūdadohā nakṣatrāṇi purīṣamāhutayaḥ samidha ādityo lokampṛṇā tadvā etatsarvamādityamevābhisampadyate tatsarvo'gnirlo

But, indeed, that Fire-altar also is the sky:--the (heavenly) waters are its enclosing-stones, for even as a case here is closed up so are these worlds (enclosed) within the waters; and the waters beyond these worlds are the enclosing-stones;--the gods are the Yagushmatî bricks; what food there is in that world is its Sûdadohas; the Nakshatras (lunar mansions) are the earth-fillings, the oblations and the fire-logs; and Âditya (the sun) is the space-filler;--thus this comes to make up the whole Agni; and the whole Agni comes to be the space-filler; and, verily, whosoever knows this, thus comes to be that whole (Agni) who is the space-filler.