Srimad Bhagavadgita Sadhaka Sanjivani -Swami Ramsukhdas
Link:- Having explained that the faith of a person can be known by his worship or by the food, which is dear to him, the Lord now explains, the three kinds of sacrifice, by which a man's faith or inclination, is known.
Sacrifice (yajna) which is performed, according to scriptural law, by those, who expect no reward and believe firmly, that it is their duty to offer the sacrifice, is sattvika (good). 11
The term 'yastavyam', denotes that sacrifices should be offered, as a duty. When a man offers sacrifice having desire of gaining honour, praise and riches here, and heaven and luxuries, in the next birth, he is attached to the sacrifice. But if he performs it, without any kind of reward, his affinity with it is renounced and (in absence of selfishness and pride), his ego is purified.
- Duty is the action which should be performed, which is according to ones capacity and by which the am is achieved.