“At no time was I non-existent, nor you, nor these people. Nor shall any of us ever cease to be hereafter.”
Through several verses in the second and thirteenth chapters, Krishna teaches Arjuna that the soul is distinct from the visible body. Soul is present in every living thing, human, animal or plant. The soul is eternal and indestructible. In Verse 23 of Chapter 2, Krishna says,
“Weapons cannot cut this (soul). Fire cannot burn this. Nor can water wet this. And the wind cannot dry this.”
The soul does not cease to exist when the body dies and is buried, burnt or eaten up. It is the body that is cast off in death just as we cast off old clothes. So, grief over death is foolish.
Thus, it was essential for Arjuna to realize the concept of the soul in order to stop agonizing over the inevitable deaths in the impending war.
Verse 2.12

Karma, in Sanskrit, means “action” or “deed” in its literal sense. Karma is equivalent to the rule of law in the spiritual world. Cause and effect must be equivalent. All acts including thoughts produce results.
Every act or thought, good or bad, has an effect on oneself. Every motion of the mind deals a stroke on one’s own character. As a consequence of one’s own action, the character evolves for the better or for the worse. The karma of an individual’s actions, positive or negative, may be experienced immediately, later in their present life, or possibly in a future life or lives. It is important to remember that an individual’s karma is based on their thoughts, words, actions, and choices.
Man evolves himself exactly according to his actions. This process is unbroken by death since the soul does not die. Karma continues to operate beyond death. The soul carries the character with it.
Karma is not fatalistic. It is not an arbitrary and external agency. In fact, it is the opposite. It places one’s evolution completely in one’s own hands.
Verse 13.20

Gita does not advise giving up action. What we should renounce is not action, but selfish desire.
A good man does the tasks to which he is called and which pertain to his place in society. He does everything without selfish motive, and maintains equilibrium of mind in success and failure, pleasure and pain, joy and sorrow.
We should perceive inaction in action, that is, renounce (inaction) selfish desire while doing work (action). We should also realize action in inaction, that is, external abstinence (inaction) alone does not mean purity of mind. Control of internal desires is true inaction.
A true Sanyasi and Yogi is one who performs action as duty, not looking forward to the results of such action. One who merely stops bodily activities cannot become one.
Verse 6.1

In chapters 2, 3, 16 and 18, Gita teaches us the importance of control of mind. Selfless performance of work is true Yoga. Control of the mind is required so that selfish attachments do not develop. If the mind is not controlled, desire will find its perch in the senses.
If a man thinks about sensual objects, it gives birth to attachments for them. Desire comes from attachment and desire gives birth to anger. Anger gives birth to delusion and delusion leads to confusion of memory. From confusion of memory comes loss of intellect and loss of intellect results in destruction.
Krishna tells Arjuna, “The cause of sin is desire, it is anger. It is born out of the principle of passion in nature, insatiable and all polluting. Know it as our enemy on earth. “
Verse 2.61

Krishna advises meditation for those who have already become a Karma-Yogi. They do their duties without selfish desire. They are not affected by the success or failure of such duties.
Having steadied the mind, controlling the thoughts and the senses, settling down on his seat, he should engage himself in meditation for purification of the self.
For those who seek the state of Yoga, performance of duty without attachment is the path. For those who have reached this stage, tranquility is the path for the state of Yoga.
Verses 6.12 and 6.13

Our minds are agitated when we constantly see evil. To calm the mind in such moments, it is important to judge others with kindness. Krishna states that he dwells in the heart of all beings. Through the force of Maya, he makes all being moves like puppets on a revolving machine.
Therefore, we should not be moved to anger or contempt if anyone commits what we deem to be wrong. We should also not pride ourselves upon our own good action. Men are moved by qualities caused by Karma; and it defeats all effort at ignoring the qualities. This is a teaching to cultivate kindness towards others and serenity in ourselves.
Note: This should not be confused with misplaced tolerance towards adharma. The Gita itself is an appeal to Arjuna to fight to protect Dharma.
Verse 18.61

In the seventh chapter, Krishna says that there are many types of humans. Among them, those who worship Krishna with true knowledge are dear to Krishna. There are also humans whose knowledge has been robbed by desires. According to their own nature, they worship other Gods and follow prescribed rites.
Then Krishna says, “Whatever form a devotee wishes to worship faithfully, in whatever way, I make the faith firm and unwavering.” Thus, it is not just an accommodation of other forms of worship, but active help to make such faith firm. Krishna protects all paths that follow the basic principles of Dharma.
Verse 7.21

The Gita recognizes the difficulty of worshipping the impersonal and Absolute. Therefore, it suggests the path of Bhakti (surrender, though it is not the perfect translation of Bhakti). Gita advises us to dedicate all our work as service to God and worship of God. This aspect of Hindu faith is known as Bhakti path of salvation.
Verse 18.65

When a man is able to regulate conduct, control the mind and dedicate all activities to God, in due course of time he realizes the oneness of existence. Differences between high and low, of one life form with another all disappear. Sages treat everyone, different humans, a cow, an elephant, a dog or even a dog-eater equally. The identification of self with all life, and all life with the divine is true Jnana.
Verse 6.29

Gita records a miracle in the 11th chapter. Arjuna is made to see the Vishwarupa. The meaning of this is that a seeker may catch a glimpse of God when he merges himself in the universe through a pure and dedicated life, serenity and meditation. He then realizes the oneness of all existence.
Verse 11.13

The first two verses of Ishopanishad are considered as the summary of Karma Yoga. Mahatma Gandhi once said that the first verse alone is enough for Hinduism to survive even if all other works disappear. Thus, Gita is not an independent work or a departure from other teachings of Hindusim.

The 63rd verse in the last chapter perhaps reflects the approach of Hinduism. It is not a rigid set of rules to be obeyed, but choices a seeker should make according to his circumstances. In this verse, Krishna tells Arjuna,
‘I have explained to you this knowledge that is the most secret of all secrets. Having examined it completely, do what you wish to do.’
Verse 18.63