Bhagavad Gita 2.31

You must look at your duty. Nothing can be more welcome to a soldier than a righteous war. Therefore, wavering in this resolve is unworthy, O Arjuna!

स्वधर्ममपि चावेक्ष्य न विकम्पितुमर्हसि।
धर्म्याद्धि युद्धाछ्रेयोऽन्यत्क्षत्रियस्य न विद्यते॥

svadharmamapi cāvekṣya na vikampitumarhasi|
dharmyāddhi yuddhāchreyo'nyatkṣatriyasya na vidyate||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).