One verse

Srimad Bhagavatam 7.11.14

7.11.14

विप्रस्याध्ययनादीनि षडन्यस्याप्रतिग्रह: । राज्ञो वृत्ति: प्रजागोप्तुरविप्राद्वा करादिभि: ॥ १४ ॥

viprasyadhyayanadini sad-anyasyapratigrahah rajno vrttih praja-goptur aviprad va karadibhih

viprasya
of the brahmana
adhyayana-adini
reading the Vedas, etc
sat
six (to study the Vedas, to teach the Vedas, to worship the Deity, to teach others how to worship, to accept charity and to give charity)
anyasya
of those other than the brahmanas (the ksatriyas)
apratigrahah
without accepting charity from others (the ksatriyas may execute the five other occupational duties prescribed for the brahmanas)
rajnah
of the ksatriya
vrttih
the means of livelihood
praja-goptuh
who maintain the subjects
aviprat
from those who are not brahmanas
va
or
kara-adibhih
by levying revenue taxes, customs duties, fines for punishment, etc

For a brahmana there are six occupational duties. A ksatriya should not accept charity, but he may perform the other five of these duties. A king or ksatriya is not allowed to levy taxes on brahmanas, but he may make his livelihood by levying minimal taxes, customs duties, and penalty fines upon his other subjects.