Man must engage in action but engage in action without desire.
कुर्वन्नेवेह कर्माणि जिजीविषेच्छतँ समाः।
एवं त्वयि नान्यथेतोऽस्ति न कर्म लिप्यते नरे॥
Kurvanneveha karmani jijeevishechchatam samah
Evam tvayi nanyathetosti na karma lipyate nare.
Meaning of mantra
All is His. This does not mean sitting idle at home shunning all work. Man must engage in action (karma) but engage in action without desire (nishkaam karma), and may desire to live in this world for 100 years while engaging in action (karma). In this way man is not covered with a coating of action (karma). Without this, there is no recourse.
Summary of the mantra
One Should wish to live a hundred years on this earth, he should live doing action or Karma. While thus, (as) man, you live, there is no way other than this by which action or Karma will not cling to you.
