After the one thousand celestial years of Kali-yuga, the Satya-yuga will manifest again. At that time the minds of all men will become self-effulgent.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
दिव्याब्दानां सहस्रान्ते चतुर्थे तु पुनः कृतम् । भविष्यति यदा नॄणां मन आत्मप्रकाशकम्
divyābdānāṃ sahasrānte caturthe tu punaḥ kṛtam | bhaviṣyati yadā nṝṇāṃ mana ātmaprakāśakam
SB 12.2.34