Śatapatha Brāhmaṇa ("of a hundred paths") 8.3.2.7

8.3.2.7

tadyadetā | atropadadhāti saṃvatsara eṣo 'gnirima u lokāḥ saṃvatsarastasyāntarikṣameva madhyamā citirantarikṣamasya varṣāśaradāvṛt tadyadetā atropadadhāti yadevāsyaitā ātmanastadasminnetatpratidadhāti tasmādetā atropadadhāti

And as to why he places these (four bricks) in this (layer),--this fire-altar is the year, and the year is the same as these worlds, and the middlemost layer is the air (-world) thereof; and the rainy season and autumn are the air (-world) thereof: hence when he places them in this (layer), he thereby restores to him (Agni) what (part) of his body these (formed),--this is why he places them in this (layer).