The fourth chapter of the Bhagavad Gita is Jnana Karma Sanyasa Yoga. In this chapter, Krishna glorifies the Karma Yoga and imparts the Transcendental Knowledge (the knowledge of the soul and the Ultimate Truth) to Arjuna. He reveals the reason behind his appearance in this material world. He reveals that even though he is eternal, he reincarnates time after time to re-establish dharma and peace on this Earth. His births and activities are eternal and are never contaminated by material flaws. Those persons who know and understand this Truth engage in his devotion with full faith and eventually attain Him. They do not have to take birth in this world again.
The four castes have been created by Me through a classification of the gunas and duties. Even though I am the agent of that (act of classification), still know Me to be a non-agent and changeless.OPEN VERSE
Actions do not taint Me; for Me there is no hankering for the results of actions. One who knows Me thus, does not become bound by actions.OPEN VERSE
Having known thus, duties were performed even by the ancient seekers of Liberation. Therefore, you undertake action itself as was performed earlier by the ancient ones.OPEN VERSE
Even the intelligent are confounded as to what is action and what is inaction. I shall tell you of that action by knowing which you will become free from evil.OPEN VERSE
For there is something to be known even about action, and something to be known about prohibited action; and something has to be known about inaction. The true nature of action is inscrutable.OPEN VERSE
He who finds inaction in action, and action in inaction, he is the wise one [Possessed of the knowledge of Brahman] among men; he is engaged in yoga and is a performer of all actions!OPEN VERSE