18.44 Svabyavajam, the natural; vaisya-karma, duties of the Vaisyas, of the Vaisya caste; are krsi-gauraksyavanijyam, agriculture, cattle rearing and trade: Krsi is tilling of land. Orre who rears cattle (go) is goraksa; the abstract form of that word is gauraksyam, animal-husbandry. Vanijyam means the occupation of a trader, consisting of buying and selling. Sudrasya, of the Sudra; api, too; svabhavajam, the natural; karma, duty; is paricaryatmakam, in the form of service. When rightly pursued, the natural result of these duties enjoined for the castes is the attainment of heaven-which act is evident from such Smrti texts as, 'People belonging to the castes and stages of life, who are true to their own duties, experience after death the fruit of their actions. And after that, as a result of the remnants of their merits they are born in some excellent region, caste and family, with greater piety, longevity, learning, conduct, wealth, happiness and intelligence' (Ap. Dh. Su. 2.2.2.3), etc. And in the Puranas also it is particularly mentioned that poeple belonging to the (different) castes and stages of life come to have specific results in the form of different worlds. But this result that is going to be stated follows from a different cause:

(Showing excerpt)

18.44 The natural duties of the Vaisyas are agriculture, cattle-rearing and trade. Of the Sudras, too, the natural duty is in the form of service.