Devibhagavatapurana 7.36.12

7.36.12

hiraṇmaye pare kośe virājaṃ brahma niṣkalam |
tacchubhraṃ jyotiṣāṃ jyotistadyadātmavido viduḥ ||

The Brahman (called Sis'umâram) free from all passions and parts (manifests in the external world) in the highest Golden Sheath (the Cosmic Egg). That is pure, that is the highest of Lights, it is that which the knowers of Âtmân know. [Note. -- "He is in the Centre of the Cosmic (as Sis'umâra, the Light of all Cosmic Suns). He is even in the centre of our Sun and illumining all planets."]
In the first respect He is meditated upon as Sis'umara and in the second as Gâyatrî." [Note.--In man, the Brahman manifests in the heart or the Auric Egg, called the city of Brahman. In the Universe, He manifests Himself in the Cosmic Egg, called the "Golden Sheath." These are the two places where Brahman may be meditated upon.
This verse has been explained in two different ways: First, as applying to S'is'umâra and secondly, as teaching how to meditate on Nârâyana in the Sun. The "Golden Sheath" would then mean the Solar sphere. The Supremely High Brahman resides in the excellent Golden Sheath. He is Pure and Without parts.]