Service of other three classes has been the fixed duty of the Shudra. Agriculture has been fixed for the Vaishyas; and fighting has been ordained for the Kshatriyas. The vow of Brahmacharya, devotion, repetition of the mantras and truthfulness are always to be observed by the Brahmanas.
कर्म शूद्रे कृषिर्वैश्ये संग्रामः क्षत्रिये स्मृतः। ब्रह्मचर्यं तपो मन्त्राः सत्यं च ब्राह्मणे सदा॥