In the fifth chapter, called "Sanyasa Yoga" or "Renunciation in the light of Yoga" Krishna examines the idea of renunciation (of action) as enjoined by the Vaiseshika, Nyaya and Sankhya systems; and He tells Arjuna that action properly performed is superior to renunciation.
He points out that both Sankhya and Yoga recognize that life is characterised by action and man cannot renounce it altogether; but when the soul is self-controlled, senses subdued and actions performed in the spirit of sacrifice, the actor receives no taint. The Sankhya system ascribes all action to Nature (Prakriti); and even if we assume that God has nothing to do with it (action), we cannot escape the necessity of action ourselves; but we can gain freedom from the bondage of action if we act as Yogis, with restrained senses, Buddhi and Mind.
Renunciation dost thou praise
The Blessed Lord said:
Renunciation, action too,
He is a true renouncer called
Children, not men of wisdom, say
The place that is by Sankhyas reached,
Renunciation's hard indeed
Whose soul is free and self controlled,
The knower of truth, intent on Yoga,
And speaks, or holds, or setteth free,
Without attachment who performs
With body, Buddhi, and the Mind,
Renouncing fruit of actions all,
The self-controlled embodied one,
The Lord for people doth create,
The Lord takes note of no one's sins,
Who have destroyed their ignorance
On That whose Buddhi's fixed and soul,
The wise behold with equal eye
Even here they conquer all the world
Whose Buddhi's steady and unperplexed,
To external objects unattached,
Pleasures that are of contact born
He who can bear within the world,
Whose joy's within, pleasure within,
Rishis who have their sins removed,
Released from anger and desire,
Excluding touch with outward things,
Restraining senses, Buddhi, Mind,
He gaineth peace who knows I am
Sankhya and Yoga are not different: Sankhya tells us that all life is based on Prakriti, which is characterized by incessant action. Hence we must perform actions whether we like them or not. Yoga, as the first aspect of Vedanta, also tells us that we must perform all actions, but as a Sacrifice.
This idea of Sacrifice is lacking in the Sankhya; and so it holds that all actions must ultimately be renounced if we seek freedom from the ills of life. Knowledge is, therefore, the final goal of the Sankhya. Yoga, however, holds to action; and that is the chief difference between them.
The city of nine gates: This is the human body, with nine gates or openings, two ears, two eyes, two nostrils, one mouth, one organ of creation, and one organ of excretion.
God, Action, Nature: Action, according to all systems of thought, except Vedanta and Yoga as its first manifestation, is said to belong to Prakriti or Nature, and not to God.
Nirvana: Final liberation or union with the Supreme. With Buddhists it is a state of utter annihilation of individual existence.