Chapter 3 Verse 21

यद्यदाचरति श्रेष्ठस्तत्तदेवेतरो जनः
स यत्प्रमाणं कुरुते लोकस्तदनुवर्तते

Because whatever noble persons do, others follow. Whatever standard they set up, the world follows. This is the meaning of this verse. So Krishna was saying here that whatever the leaders did, the devotees or people below will follow. So the leader has to set up an example. Krishna asked Arjuna, why should I come here and talk to you in a battle field? I can have nice fun with my flute, etc. I am here as a charioteer for you in the battle field, and giving you the knowledge and convincing you to fight. I personally have nothing to accomplish but I am doing this for loka sangrahaha i.e. for the well-being. I am fullness personified and there is nothing for me to achieve yet, I am active and involve myself in activities. So Arjuna, you will have to expand your vision of not just looking at yourself but what you have to do for community at large. That’s what I am doing here by being a messenger to you, a charioteer, a guide to you and also explaining the values to you so that general mankind will benefit from my teaching.

By the responsibility of maintaining the social order, upholding dharma, and not to mislead people, I am doing this karma even though I am above all this. I am the lord myself and my role is to preserve and bless the beings, how can I not indulge in an activity where I know that dharma is not steady, the order is not there. Even as a man of vision, there is no necessity to do anything because he or she is a wise person. But for the atma nothing is to be done, even then the activity is to be done for blessing others and not just for one’s own purpose.