Lord Krsna summed up the main theme of this fourth chapter which is jñāna-karma-sannyāsa (the renunciation of action through knowledge).
yogasannyastakarmāṇaṃ jñānasaṃcchinnasaṃśayam |
ātmavantaṃ na karmāṇi nibadhnanti dhanañjaya ||4.41||
Dhanañjaya (Arjuna)! Actions do not bind the one who has renounced action through yoga, whose doubts has been completely severed by knowledge (and) the one who is together.
Here Lord Krsna addresses Arjuna as Dhanañjaya as the one who has earned number of titles and all kind of wealth. For earning these, he has to do a lot of karma (actions). But with all these karma (together with their results), can one still be free? Yes.
na karmāṇi nibadhnanti - none of the actions bind the person. Actions here include all types of actions, proper and improper acts, Vedic rituals, and all worldly activities. Who is the one not bound by actions? Three qualifications are given here for such a person.
First, yoga-sannyasta-karmāṇaṃ - one who has given up action as a non-doer through yoga characterised by the clear vision of reality. Yoga here refers to jñāna-yoga (self knowledge). Only through the clear vision of I am sat-cit-ānanda ātmā illumines all actions but not bound by them, then one can be said to be renounced all actions. This is the central theme of this chapter. Even though knowledge alone frees oneself, but karma-yoga as the qualification for ātma-jñāna is included here. In order for the knowledge to be abide, one should live a life of karma-yoga.
jñānasaṃcchinnasaṃśayam - one whose doubts have been completely severed by knowledge. In previous qualification, one's doer-ship and enjoyer-ship have been negated by knowledge. But this knowledge of the self has to be doubtless. What kind of doubts are there? One might doubt whether fullness is the real nature of myself, or is it really no division between me, the Lord and entire world? We may have conviction while we are in the Vedānta class, but when we step out of the class and encounter some problem, seems like we all forget about the teaching. Therefore knowledge needs to be abided firmly without doubts.
We have talked about śraddhā towards śāstra in verse 4-39. This faith in the śāstra as pramāna (means of knowledge about the self) is required only until knowledge takes place, then one become free from all doubts that only I ātmā is satyam (independent reality) and anātma is mithya (dependent reality). With reference to heaven and so on, even though mentioned by śāstra, the statements are not verifiable here, we only have faith for it. But when we are talking about the self, the self-evident "I", I do not need śāstra to tell me that "I am" (I am aware of my own existence). Śāstra is required only to correct the wrong notions or conclusions that I have about myself. That "I am" is a self-evident is a fact, it is not a conclusion, whereas "I am a samsārī" is a conclusion. This conclusion is purely notional, and is absent when I am asleep, is absent between two thoughts, is absent in a moment of joy, and is falsified in the wake of the knowledge. I do not need to verify that "I am" and that "I exist". I need to only eliminate the doubts and the errors about myself. Śāstra enables me do this.
The removal of wrong notion about oneself is what ātma-jñana does, knowledge of the identity of the self with Īśvara. And the one whose doubts have been removed by this knowledge is called jñānasaṃcchinnasaṃśayah.
ātmavantaṃ, one who is together, which is explained how the removal of doubts and error is achieved. One who is together means one who has the body-mind-sense-complex under one's control, and his/her habitual error also being removed.
Next Lord Krsna concludes the chapter by urging Arjuna to take to action with an attitude of karma-yoga, which will lead him to knowledge.
tasmādajñānasambhūtaṃ hṛtsthaṃ jñānāsinātmanaḥ |
chittvainaṃ saṃśayaṃ yogamātiṣṭhottiṣṭha bhārata ||4.42||
Therefore, Bhārata (Arjuna)! slaying with the sword of knowledge this doubt about the self, which is born of ignorance, which is rooted in the mind, get up (and) take to yoga (karma-yoga).
yogam ātiṣṭha - take to yoga, which means karma-yoga which leads to knowledge. When one lives a life of karma-yoga, the knowledge will face no obstruction. Only when correct knowledge takes place, then wrong notion about oneself which is the cause of samsāra will go away. And this wrong notion is taking place in the mind - hṛtsthaṃ, indicate that knowledge is the solution.