Ramayana
ततस्त्रेतायुगं नाम मानवानां वपुष्मताम् । क्षत्रियास्तत्र जायन्ते पूर्णेन तपसा ऽन्विताः ॥ 7-74-11 ॥
Then came the age called Treta, the age of men endowed with bodies; in it kshatriyas were born, possessed of the full measure of austerity.
english translation