Ramayana
त्रेतायुगे च वर्तन्ते ब्राह्मणाः क्षत्रियाश्च ये । तपो ऽतप्यन्त ते सर्वे शुश्रूषामपरे जनाः ॥ 7-74-20 ॥
In the Treta age the brahmins and kshatriyas who lived therein, all of them practiced austerity, while the other people rendered service.
english translation