One verse

Srimad Bhagavatam 10.24.20

10.24.20

वर्तेत ब्रह्मणा विप्रो राजन्यो रक्षया भुव: । वैश्यस्तु वार्तया जीवेच्छूद्रस्तु द्विजसेवया ॥ २० ॥

varteta brahmaṇā vipro rājanyo rakṣayā bhuvaḥ vaiśyas tu vārtayā jīvec chūdras tu dvija-sevayā

varteta
lives
brahmaṇā
by the Vedas
vipraḥ
the brāhmaṇa
rājanyaḥ
the member of the ruling class
rakṣayā
by protection
bhuvaḥ
of the earth
vaiśyaḥ
the vaiśya
tu
on the other hand
vārtayā
by trade
jīvet
lives
śūdraḥ
the śūdra
tu
and
dvija-sevayā
by serving the twice-born brāhmaṇas, kṣatriyas and vaiśyas.

The brāhmaṇa maintains his life by studying and teaching the Vedas, the member of the royal order by protecting the earth, the vaiśya by trade, and the śūdra by serving the higher, twice-born classes.