Then Vairāja Brahmā, the soul of the universal form, gives up his universal body, O King, and enters into the subtle unmanifest nature, like a fire that has run out of fuel.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
ततो विराजमुत्सृज्य वैराजः पुरुषो नृप । अव्यक्तं विशते सूक्ष्मं निरिन्धन इवानलः
tato virājamutsṛjya vairājaḥ puruṣo nṛpa | avyaktaṃ viśate sūkṣmaṃ nirindhana ivānalaḥ
SB 11.3.12