SB 12.2.23

yadāvatīrṇo bhagavān
 kalkir dharma-patir hariḥ
kṛtaṁ bhaviṣyati tadā
 prajā-sūtiś ca sāttvikī
Synonyms: 
yadā — when; avatīrṇaḥ — incarnates; bhagavān — the Supreme Lord; kalkiḥ — Kalki; dharma-patiḥ — the master of religion; hariḥ — the Supreme Personality of Godhead; kṛtam — Satya-yuga; bhaviṣyati — will begin; tadā — then; prajā-sūtiḥ — the creation of progeny; ca — and; sāttvikī — in the mode of goodness.
Translation: 
When the Supreme Lord has appeared on earth as Kalki, the maintainer of religion, Satya-yuga will begin, and human society will bring forth progeny in the mode of goodness.