Better is one's own duty (though) destitute of merits, than the duty of another well performed. He who does the duty ordained by his own nature incurs no sin.
In simple words
Krishna repeats one of the Gita's core principles: "It is better to do your own work imperfectly than to do someone else's work perfectly. When you do the work that matches your own nature, you cannot go wrong."
Word-by-word meanings
श्रेयान्betterस्वधर्मःones own dutyविगुणः(though) destitute of meritsपरधर्मात्that the duty of anotherस्वनुष्ठितात्(than) well performedस्वभावनियतम्ordained by his own natureकर्मactionकुर्वन्doingनnotआप्नोति(he) incursकिल्बिषम्sin
18.47 श्रेयान् better? स्वधर्मः ones own duty? विगुणः (though) destitute of merits? परधर्मात् that the duty of another? स्वनुष्ठितात् (than) well performed? स्वभावनियतम् ordained by his own nature? कर्म action? कुर्वन् doing? न not? आप्नोति (he) incurs? किल्बिषम् sin.Commentary Just as a poisonous substance does not harm the worm born in that substance? so he who does his Svadharma (the duty ordained according to his own nature) does not incur any sin.What is poison to the whole world is sweet to a worm and yet sugarcane juice that is sweet causes its death. So a mans appointed duty which frees him from bondage must? therefore? be practised however difficult it may seem to be. If you try to do the duty of another it will bring,danger. He who has no knowledge of the Self cannot remain even for a moment without doing action. (Cf.III.35)
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
# BG 18.47 — Commentary Translation
The detailed discussion of the first line of this verse has already been undertaken in the Third Chapter. By one's own dharma is meant one's own varna and the duties prescribed by it. The term varna has been clarified. It is observed that due to attachment and aversion in the human mind, one's own work may appear deficient in quality while another's work may seem superior. When such a sentiment arises in the mind, one abandons one's own dharma and becomes engaged in the practice of another's dharma. Yet, because it goes against one's nature, one fails in that new undertaking, and moreover, the bondage of attachments and aversions—that is, the bondage of desires—becomes even more firmly established in the mind. Therefore, the Bhagavan says: Even though devoid of merit when imperfectly performed, the observance of one's own dharma is superior to the well-executed dharma of another.
The performance of action according to one's nature does not incur sin or transgression. This means that the observance of one's own dharma does not generate new binding desires.
This final chapter of the Gita is the conclusion of the Bhagavan Sri Krishna's beautiful discourse. Thus, it is natural that it contains the essence of the entire Gita. In the preceding chapters, the principal doctrines that were discussed for the remedy of Arjuna's affliction are here reiterated.
The reasoning given in the teaching of dharma observance is this: the performance of one's own actions does not become the cause of sin, even though there may be some defects in it. This should be understood in the following manner: (1) The venom of a poisonous serpent does not destroy the serpent itself; (2) The living microorganisms dwelling in wine do not themselves become intoxicated; and (3) The mosquitoes carrying malaria do not themselves suffer from malaria. Similarly, no person's nature is defective or harmful for them. However, if the serpent's venom were mixed with wine, those microorganisms would be destroyed. In exactly the same way, if a Kshatriya engages in the duties of a Brahmin, he will bring about his own destruction. Arjuna was a Kshatriya. Without the purity of sattva guna, had he gone to the forests to practice meditation, he would never have succeeded in it.
In summary: there is no benefit in engaging in a field of action contrary to one's nature. In this world, every thing has its appointed place. Every creature and every person has their own significance, and no one is contemptible, for each person is capable of performing some particular work that another cannot perform. In the creation of the Almighty, there is neither excess nor futility anywhere. Not even a single blade of grass has been brought forth without purpose in any time or place.
Should one observe one's duty even when it is defective? The Bhagavan answers: