Thereafter, at the conjunction of two yugas, the Lord of the creation will take His birth as the Kalki incarnation and become the son of Viṣṇu Yaśā. At this time almost all the rulers of the earth will have degenerated into plunderers.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अथासौ युगसन्ध्यायां दस्युप्रायेषु राजसु । जनिता विष्णुयशसो नाम्ना कल्किर्जगत्पतिः
athāsau yugasandhyāyāṃ dasyuprāyeṣu rājasu | janitā viṣṇuyaśaso nāmnā kalkirjagatpatiḥ
SB 1.3.25