Unsteady, vulgar, unbending, cheating, malicious, lazy, desponding and procrastinating such an agent is called Tamasic.
In simple words
Krishna describes a dark doer: "A person who is unfocused, crude, stubborn, dishonest, mean-spirited, lazy, depressed, and always putting things off — that person is a dark doer."
Word-by-word meanings
अयुक्तःunsteadyप्राकृतःvulgarस्तब्धःunbendingशठःcheatingनैष्कृतिकःmaliciousअलसःlazyविषादीdespondingदीर्घसूत्रीprocrastinatingचandकर्ताagentतामसःTamasic (dark)उच्यतेis said
18.28 अयुक्तः unsteady? प्राकृतः vulgar? स्तब्धः unbending? शठः cheating? नैष्कृतिकः malicious? अलसः lazy? विषादी desponding? दीर्घसूत्री procrastinating? च and? कर्ता agent? तामसः Tamasic (dark)? उच्यते is said.Commentary Owing to his vulgar nature he is not able to discriminate between proper and improper actions. His heart is filled with vanity. He will never prostrate himself before the deity or a sage. He is very stiff and unbending in his demeanour. He is the very embodiment of deceit? the abode of the passion for gambling and all such vices. He is ever ready to do evil actions. When an opportunity for his doing good occurs? he is utterly slothful and inactive? but he is very alert in doing evil.Prakritah Vulgar Quite uncultured in intellect one who is childish.Stabdhah Unbending (like a stick)? not bowing down to anybody.Shathah Cheating concealing his real nature.Naishkritikah Creating arrels and disputes among the people.Alasah Lazy Not doing even that which ought to be done.Dirghasutri Postponing duties too long always slothful not performing even in a month what ought to be done today or tomorrow.
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
Here, the tamasic agent impelled by tamasic knowledge performing tamasic action is described in detail. The unintegrated one—whose mind is not united with wisdom is called unintegrated. Neglecting the guidance of wisdom, the tamasic agent acts according to his own whims. The uncultured one—a person of extremely crude and unrefined intellect is called uncultured. The refined person is one who keeps the base tendencies of his mind under control. But the tamasic person, being unintegrated, is of crude nature. He has no self-restraint whatsoever. Even when the mirror of wisdom shows him his reflection, he does not accept that the uncouthness and other defects reflected in that mirror are his own. The stubborn one—like a wooden post, he never bows humbly before anyone. He is so obstinate and rigid that he does not even wish to listen to anyone's good counsel, let alone follow it. He cannot bear any instruction from anyone.
The deceitful one—that is, the deceptive one. The tamasic agent can never be trusted, because he conceals his true intentions and deceives people by engaging in other kinds of activities. Through such deceptive acts, people in society suffer pain and hardship.
The destructive one—Sri Shankara explains this: the tamasic agent is one who destroys others' livelihoods. He is always ready to quarrel and fight with others and harbors enmity and a spirit of revenge.
The lazy one—the tamasic agent does not readily engage in any work, not even in obligatory duties. He desires to enjoy the fruits without exertion. Such a lazy person is incapable even of reflection. The three brothers of Lanka—Vibhishana, Ravana, and Kumbhakarna—are respectively symbols of sattvic, rajasic, and tamasic agents.
The despondent one—always remains dejected. He is never satisfied with anything or anyone. He lacks both the capacity and the firmness to face life's challenges. Therefore, he wishes to dwell in some safe place where there are no worldly problems and he can indulge in sense pleasures unobstructed.
The procrastinator—the person who says he will do tomorrow what should be done today, and even after a month does not do it, is called a procrastinator. He cannot make quick decisions, and even if he does make them, he cannot execute them.
Thus, in three verses, Lord Sri Krishna has painted a most beautiful portrait of the inner nature of the three types of agents. It should always be remembered that the above description is not for judging others, but for self-examination and self-improvement.
The Lord further says—