Triple is the gate of this hell, destructive of the self lust, anger and greed; therefore one should abandon these three.
In simple words
Krishna names the three gates that lead to self-destruction: "Lust, anger, and greed — these three are the doors to darkness and the destruction of the soul. A person must abandon all three."
Word-by-word meanings
त्रिविधम्tripleनरकस्यof hellइदम्thisद्वारम्gateनाशनम्destructiveआत्मनःof the selfकामःlustक्रोधःangerतथाalsoलोभःgreedतस्मात्thereforeएतत्thisत्रयम्threeत्यजेत्(one) should abandon
16.21 त्रिविधम् triple? नरकस्य of hell? इदम् this? द्वारम् gate? नाशनम् destructive? आत्मनः of the self? कामः lust? क्रोधः anger? तथा also? लोभः greed? तस्मात् therefore? एतत् this? त्रयम् three? त्यजेत् (one) should abandon.Commentary Lust? anger and greed? -- these highway robbers will cause a man to fall into the dark abyss of hell? misery or grief. These are the three fountainheads of misery. These three constitute the gateway leading to the lowest of hells. These are the enemies of peace? devotion and knowledge. When these evil modifications of the mind arise in it? man loses his balance or poise and discrimination and commits various evil actions.Lust? anger and greed denote selfblindness and ignorance? for there are no Vasanas? wants? anger? or greed in Brahman or the pure immortal Self.Narakasya dvaram The gate to hell The gate leading to hell. The self is destroyed by merely entering at the gate? i.e.? it is not fit to do any right exertion to attain the goal of life.As this gate causes selfdestruction? let everyone renounce these three. (Cf.III.47)In the next verse the man who has abandoned these three evils is highyl eulogised.
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
Heaven is the form of happiness, and hell is the form of suffering. Therefore, even in this very life, a human being can experience heaven and hell in the state of their own mind. Through the authority of scripture, one gains knowledge of the existence of both heaven and hell. In this verse, three gates of hell are described. The purpose of this entire chapter is to deliver humanity from the demoniac state and grant them the experience of selfless service and the bliss of the atman.
Desire, anger, and greed—where desire exists, anger naturally follows. When one continuously contemplates upon an object, believing it to be a means of happiness, desire for that object is born. If any obstacle comes in the fulfillment of this desire, anger arises from it. If the desire is intense, then anger becomes so fierce that it tosses the boat of life hither and thither, shatters it into pieces, and finally drowns it.
When desire is fulfilled, a person's greed continues to grow, and in this way, their strength diminishes. That feeling of dissatisfaction which poisons our sense of present contentment is called greed. A greedy person never attains peace and happiness, because dissatisfaction is the very nature of greed.
If we understand this cycle of action and reaction between desire, anger, and greed, then we must accept the conclusion of the Bhagavan—that these three should therefore be renounced.
In praise of the renunciation of these three, it is said: