The transcendental Supreme Person, the Supersoul of all living entities, who are in different statuses of life, high and low, existed at the end of the millennium, when neither this manifested cosmos nor anything else but Him existed.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
परावरेषां भूतानामात्मा यः पुरुषः परः । स एवासीदिदं विश्वं कल्पान्तेऽन्यन्न किञ्चन
parāvareṣāṃ bhūtānāmātmā yaḥ puruṣaḥ paraḥ | sa evāsīdidaṃ viśvaṃ kalpānte'nyanna kiñcana
SB 9.1.8