Chapter 4 – JnanaYoga
evaṁ jñātvā kṛtaṁ karma
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Knowing this the people who were liberated performed their work. You also perform your work like your predecessors.
One who gets to know about God(like how he is unchanging, non-doer, and does it without any desire for karma-phala) will never get entangled in their own karma. God cannot be attained with our material pursuits. Even if you strive hard and become the ruler of the earth, you cannot attain the Supreme. One day when you die you’ll have to leave behind everything you’ve attained on this earth. This was known to the liberated souls, and they performed their duties with this knowledge.
Sri Krishna tells Arjuna to follow what they did and do his duties similarly.