Ramayana
एवं कृत्वा विधानं स सन्दिदेश वसं तदा । धर्मनित्यः प्रजाः पुत्र क्षत्रधर्मेण पालय ॥ 7-54-13 ॥
Having made this arrangement, he then gave his command to Vasu: Ever steadfast in righteousness, my son, protect the subjects according to the duty of a Kshatriya.
english translation