One verse

Srimad Bhagavatam 12.3.28

12.3.28

यदा कर्मसु काम्येषु भक्तिर्यशसि देहिनाम् । तदा त्रेता रजोवृत्तिरिति जानीहि बुद्धिमन् ॥ २८ ॥

yadā karmasu kāmyeṣu bhaktir yaśasi dehinām tadā tretā rajo-vṛttir iti jānīhi buddhiman

yadā
when
karmasu
in duties
kāmyeṣu
based on selfish desire
bhaktiḥ
devotion
yaśasi
in honor
dehinām
of the embodied souls
tadā
then
tretā
the age of Tretā
rajaḥ-vṛttiḥ
predominated by activities in the mode of passion
iti
thus
jānīhi
you should understand
buddhi-man
O intelligent King Parīkṣit

O most intelligent one, when the conditioned souls are devoted to their duties but have ulterior motives and seek personal prestige, you should understand such a situation to be the age of Tretā, in which the functions of passion are prominent.