Even if I am slain, O Madhusudana (Krishna), I would not wish to kill these people; even for the sake of the three worlds; how then for the sake of a kingdom on earth!
Arjuna was not speaking in a fit of reluctance or sorrow. He makes it clear that his mind will not be tempted by any external, material reward. Even for winning the three worlds, he would not think of killing the kith and kin as well as elders. What then to speak of the limited aim of gaining Indraprastha, a small kingdom on earth?
Was Arjuna thinking selfishly, narrowly, not concerned about his brothers and so many others related to them all?
Yudhishthira and the others had placed a great deal of reliance on Arjuna, his fighting skill and potential. But at the moment, all that has no place in Arjuna’s heart and mind. The prospect of killing so many relatives, friends and elders, particularly the most beloved grandfather and the most respected teacher, was weighing so heavily in his mind that he did not think of any other factors at all.
He felt that the war was motivated by the thought of getting back their kingdom. Even if the three worlds would be won over, he felt he would not fight this war.