Bhagavatapurana 1.3.25

1.3.25

athāsau yugasandhyāyāṃ dasyuprāyeṣu rājasu /
janitā viṣṇuyaśaso nāmnā kalkirjagatpatiḥ //

25. Next, at the juncture of the two Yugas when Kings will mostly be thieves, the Supreme Lord of the world will be born of a Brahmin, Vishnu Yasas, under the name of Kalki. 26. The Avataras of Hari, the abode of all power (Satva), are countless indeed, O Brahmins, just as thousands of currents flow from a lake that never dries (and is ever full.)