santu's reply to ba:-
Karmanyewadhikaraste ma faleshu kadachan
ma karm phal heturbhur ma te sangostvakarmani.
Meaning:- [not let reward be the reason for the motivation of their activities. We must perform all of our actions without being motivated by the fruit.
It may be postulated that since the results of all actions are attained simply by worshipping the Supreme Lord, what is the use of any other actions other than devotion to Him?
To counter this conclusion the Supreme Lord states that all living entities have the right to perform actions but none have the right to claim the results.
An aspirant of the highest knowledge must know that to hanker or yearn for reward for one's actions is the cause of bondage in the material existence.
But it may be said that all actions produce a result, just as eating satisfies the urge of hunger.
Anticipating this question the Supreme Lord states that one should not let the anticipated results of actions be the cause of motivation.
Be not one who is controlled by fruitive desires.
As heaven is attained only when desired being connected to the living entity who performed the rites in the scriptures to attain such an end it can be seen that what is not desired does not take place.
Then on the other hand although fruitive actions are binding be not attached and not devoted from fear of this bondage to inaction. This is the idea of this verse.