One verse

Srimad Bhagavatam 12.2.39

12.2.39

कृतं त्रेता द्वापरं च कलिश्चेति चतुर्युगम् । अनेन क्रमयोगेन भुवि प्राणिषु वर्तते ॥ ३९ ॥

kṛtaṁ tretā dvāparaṁ ca kaliś ceti catur-yugam anena krama-yogena bhuvi prāṇiṣu vartate

kṛtam
Satya-yuga
tretā
Tretā-yuga
dvāparam
Dvāpara-yuga
ca
and
kaliḥ
Kali-yuga
ca
and
iti
thus
catuḥ-yugam
the cycle of four ages
anena
by this
krama
sequential
yogena
pattern
bhuvi
in this world
prāṇiṣu
among living beings
vartate
goes on continuously

The cycle of four ages — Satya, Tretā, Dvāpara and Kali — continues perpetually among living beings on this earth, repeating the same general sequence of events.