Sudras must work; sometimes they should engage in occupational duties as cloth manufacturers, weavers, blacksmiths, goldsmiths, brass-smiths, and so on, or else they should engage in hard labor to produce food grains
SB Canto 7
Even if one is a householder rather than a brahmacārī, a sannyāsī or a vānaprastha, one should not endeavor very hard for religiosity, economic development or satisfaction of the senses. Even in householder life, one should be satisfied to maintain body and soul together with whatever is available with minimum endeavor, according to place and time, by the grace of the Lord. One should not engage oneself in ugra-karma.
In human life there are four principles to be fulfilled-dharma, artha, kāma and mokṣa (religion, economic development, sense gratification, and liberation). First one should be religious, observing various rules and regulations, and then one must earn some money for maintenance of his family and the satisfaction of his senses. The most important ceremony for sense gratification is marriage because sexual intercourse is one of the principal necessities of the material body. Yan maithunādi-gṛhamedhi-sukhaṁ hi tuccham (SB 7.9.45). Although sexual intercourse is not a very exalted requisite in life, both animals and men require some sense gratification because of material propensities. One should be satisfied with married life and not expend energy for extra sense gratification or sex life.
As for economic development, the responsibility for this should be entrusted mainly to the vaiśyas and gṛhasthas. Human society should be divided into varṇas and āśramas-brāhmaṇa, kṣatriya, vaiśya, śūdra, brahmacarya, gṛhastha, vānaprastha and sannyāsa. Economic development is necessary for gṛhasthas. Brāhmaṇa gṛhasthas should be satisfied with a life of adhyayana, adhyāpana, yajana and yājana—being learned scholars, teaching others to be scholars, learning how to worship the Supreme Personality of Godhead, Viṣṇu, and also teaching others how to worship Lord Viṣṇu, or even the demigods. A brāhmaṇa should do this without remuneration, but he is allowed to accept charity from a person whom he teaches how to be a human being. As for the kṣatriyas, they are supposed to be the kings of the land, and the land should be distributed to the vaiśyas for agricultural activities, cow protection and trade. Śūdras must work; sometimes they should engage in occupational duties as cloth manufacturers, weavers, blacksmiths, goldsmiths, brass-smiths, and so on, or else they should engage in hard labor to produce food grains.
These are the different occupational duties by which men should earn their livelihood, and in this way human society should be simple. At the present moment, however, everyone is engaged in technological advancement, which is described in Bhagavad-gītā as ugra-karma—extremely severe endeavor. This ugra-karma is the cause of agitation within the human mind. Men are engaging in many sinful activities and becoming degraded by opening slaughterhouses, breweries and cigarette factories, as well as nightclubs and other establishments for sense enjoyment. In this way they are spoiling their lives. In all of these activities, of course, householders are involved, and therefore it is advised here, with the use of the word api, that even though one is a householder, one should not engage himself in severe hardships. One's means of livelihood should be extremely simple. As for those who are not gṛhasthas—the brahmacārīs, vānaprasthas and sannyāsīs—they don't have to do anything but strive for advancement in spiritual life. This means that three fourths of the entire population should stop sense gratification and simply be engaged in the advancement of Kṛṣṇa consciousness. Only one fourth of the population should be gṛhastha, and that should be according to laws of restricted sense gratification. The gṛhasthas, vānaprasthas, brahmacārīs and sannyāsīs should endeavor together with their total energy to become Kṛṣṇa conscious. This type of civilization is called daiva-varṇāśrama. One of the objectives of the Kṛṣṇa consciousness movement is to establish this daiva-varṇāśrama, but not to encourage so-called varṇāśrama without scientifically organized endeavor by human society.