Bhagavad Gita 18.44कृषिगौरक्ष्यवाणिज्यं वैश्यकर्म स्वभावजम्।परिचर्यात्मकं कर्म शूद्रस्यापि स्वभावजम् ॥

When a man performs his duties rightly according to his caste and order of life his heart is purified and he goes to heaven. Apastambha Dharma Sutra declares, Men of severla,castes and orders, each devoted to his respective duties, reap the fruits of their actions after death, and then by the residual Karma attain to births in superior Dharma, span of life, learning, conduct, wealth, happiness and intelligence (2,2,2,3). There is a vivid description in the Puranas also of the different results and worlds which men of the four castes and orders obtain by discharging their respective duties.