Manusmriti

siva.sh/manusmriti/11/235

ब्राह्मणस्य तपो ज्ञानं तपः क्षत्रस्य रक्षणम् । वैश्यस्य तु तपो वार्ता तपः शूद्रस्य सेवनम् ॥ २३५ ॥

sanskrit

(The pursuit of sacred) knowledge is the austerity of a Brahmana, protecting (the people) is the austerity of a Kshatriya, (the pursuit of) his daily business is the austerity of a Vaisya, and service the austerity of a Sudra.

english translation

brAhmaNasya tapo jJAnaM tapaH kSatrasya rakSaNam | vaizyasya tu tapo vArtA tapaH zUdrasya sevanam || 235 ||

hk transliteration by Sanscript