Agriculture, cow-protection, and trade, are the action (karma) of a merchant (vaiśya), born of his own nature (svabhāva). And action consisting of service, is the action of a laborer (śūdra), born of his own nature.
Farming, herding cattle, and commerce are intrinsic to the action of a commoner; action that is essentially service is intrinsic to the servant.
(44) To till the fields, protect the kine, and engage in trade, [these] are the works of peasants-and-artisans, inhering in their nature; but works whose very soul is service inhere in the very nature of the serf.
18.44 The natural duties of the Vaiśyās are agriculture, cattle-rearing and trade. Of the Śūdras, too, the natural duty is in the form of service.
18.44 Agriculture, cattle-breeding and trade are the duties of the Vaiśya born of his nature... And the duty of a Śūdra is one of service, born of his nature.
18.44 Agriculture, cattle-rearing and trade are the duties of the Vaiśya (merchant), born of (their own) nature; and action consisting of service is the duty of the Śūdra (servant-class), born of (their own) nature.