Brihadaranyaka Upanishad 6.2.9

6.2.9

asau vai loko'gnirgautama tasyāditya eva samidraśmayo dhūmo'hararcirdiśo'ṅgārā avāntaradiśo visphu-liṅgāstasminnetasminnagnau devāḥ śraddhāṃ juhvati tasyā āhutyai somo rājā saṃbhavati

'The altar (fire), O Gautama, is that world (heaven); the fuel is the sun itself, the smoke his rays, the light the day, the coals the quarters, the sparks the intermediate quarters. On that altar the Devas offer the sraddhâ libation (consisting of water). From that oblation rises Soma, the king (the moon).