The Supreme Lord, Viṣṇu, is brilliant like the sun and is known as Kṛṣṇa. When He returned to the spiritual sky, Kali entered this world, and people then began to take pleasure in sinful activities.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
विष्णोर्भगवतो भानुः कृष्णाख्योऽसौ दिवं गतः । तदाविशत्कलिर्लोकं पापे यद्रमते जनः
viṣṇorbhagavato bhānuḥ kṛṣṇākhyo'sau divaṃ gataḥ | tadāviśatkalirlokaṃ pāpe yadramate janaḥ
SB 12.2.29