Arjun Vishaad Yog-Bhagavad Gita Chapter 1 [Observing the Armies on the Battlefield of Kurukshetra]
Arjun Said > Shaloka: 38
O Janardana, although these men, overtaken by greed, see no fault in killing one’s family or quarreling with friends, why should we, with knowledge of the sin, engage in these acts?
A ksatriya is not supposed to refuse to battle or gamble when he is so invited by some rival party. Under such obligation, Arjuna could not refuse to fight because he was challenged by the party of Duryodhana. In this connection, Arjuna considered that the other party might be blind to the effects of such a challenge. Arjuna, however, could see the evil consequences and could not accept the challenge. Obligation is actually binding when the effect is good, but when the effect is otherwise, then no one can be bound. Considering all these pros and cons, Arjuna decided not to fight.