Ramayana
क्षत्रं ब्रह्ममुखं चासीद्वैश्याः क्षत्रमनुव्रताः । शूद्राः स्वधर्मनिरतास्त्रीन्वर्णानुपचारिणः ॥ १-६-१९
The kshatriyas were obedient to brahmins and vaisyas followed kshatriyas. Sudras assisted the three castes and all were fully occupied in their respective professions. ॥ 1-6-19॥
english translation
kSatraM brahmamukhaM cAsIdvaizyAH kSatramanuvratAH । zUdrAH svadharmaniratAstrInvarNAnupacAriNaH ॥ 1-6-19
hk transliteration by Sanscript