Agriculture, cattle-rearing and trade are the duties of the Vaisya (merchant), born of (their own) nature; and action consisting of service is the duty of the Sudra (servant-class), born of (their own) nature.
In simple words
Krishna describes the natural roles of merchants and workers: "Farming, raising animals, and trade come naturally to merchants. Service and practical work come naturally to workers."
Word-by-word meanings
कृषिगौरक्ष्यवाणिज्यम्agriculture cattlerearing and tradeवैश्यकर्मthe duties of Vaisyaस्वभावजम्born of natureपरिचर्यात्मकम्consisting of serviceकर्मactionशूद्रस्यof the Sudraअपिalsoस्वभावजम्born of nature
18.44 कृषिगौरक्ष्यवाणिज्यम् agriculture? cattlerearing and trade? वैश्यकर्म the duties of Vaisya? स्वभावजम् born of nature? परिचर्यात्मकम् consisting of service? कर्म action? शूद्रस्य of the Sudra? अपि also? स्वभावजम् born of nature.Commentary 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.
Contemporary scholarly and practical interpretations for modern seekers.
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
Modern
Each human being possesses the qualities of nature in a particular proportion, and therefore each person has their own distinctive nature. For this reason, the specific work that one person can perform with skill, another person cannot perform with equal proficiency. It is not possible for a warrior of passionate nature to practice meditation as a sage of pure nature does. Similarly, merchants and laborers cannot perform the courageous deeds of warriors. In social life, not all people can receive equal opportunity to reach the highest positions of honor. Yet a social order can provide equal opportunity for all people to develop according to their own nature. To make this principle or system successful, different duties have been prescribed for people of different temperaments and stations in life.
A person of merchant nature can free themselves from their faults through earnest and inspired work in agriculture, cattle-rearing, and commerce. Freedom from faults means the diminishment of desires. They have a natural inclination toward commercial pursuits. Similarly, serving all with the spirit of dedication is the natural duty of the laborer.
Each person's station and duty can be determined according to their inner nature. When a person is assigned work contrary to their nature, they not only create disorder in that field of work, but also harm themselves. For example, if a warrior were asked to fan someone with devotion, they might humbly accept it, but immediately thereafter, following their nature, they would command someone else to bring the fan. Similarly, if a merchant were made a temple priest, that sacred place would soon become lower than a commercial center, and if royal power were entrusted to them, they would be compelled by their nature to begin conducting profitable trade through that authority—what the people call corruption.
We should all determine our own station and duty through self-examination. No person of higher station has the right to look with disrespect upon those of lower stations. Each person serves society according to their capacity. While serving society with the spirit of dedication to the Divine, every person should remain engaged in the pursuit of self-development and the attainment of perfection.
On this very subject, Lord Sri Krishna speaks: