Bhagavad Gita

ಸ್ವಧರ್ಮಮಪಿ ಚಾವೇಕ್ಷ್ಯ ನ ವಿಕಂಪಿತುಮರ್ಹಸಿ ।
ಧರ್ಮ್ಯಾದ್ಧಿ ಯುದ್ಧಾಚ್ಛ್ರೇಯೋSನ್ಯತ್ ಕ್ಷತ್ರಿಯಸ್ಯ ನ ವಿದ್ಯತೇ ॥೩೧॥
svadharmamapi cāvekṣya na vikaṃpitumarhasi |
dharmyāddhi yuddhācchreyoSnyat kṣatriyasya na vidyate ||31||

Gist of the sloka:
Do not hesitate, for the primary duty of the kshatriya is to fight for dharma. When such an opportunity presents itself, one should not wait.
Sanathana dharma says, one should fight evil/adharma. Kshatriya dharma says anyone who has kshatriya lineage should stand up for righteousness and fight evil. Samaja [Kula] dharma says one should protect the common people from evil forces and if necessary stand up against it.
Arjuna being a kshatriya, a Gynani [knowledgeable person with awareness of Sanathana dharma] and being responsible as a protector of the society should do what all the three types of dharma indicates – fight the forces of evil for greater protection of the society.
Such an opportunity is rare and is eagerly sought for by kshatriyas. For right action during such time brings both fame and heaven, to the performer.