Bhagavad Gita 1.37

We are worthy of a nobler feat than slaughtering our relatives—the sons of Dhritarashtra; for, my Lord, how can we be happy if we kill our kinsmen?

तस्मान्नार्हा वयं हन्तुं धार्तराष्ट्रान्स्वबान्धवान्।
स्वजनं हि कथं हत्वा सुखिनः स्याम माधव॥

tasmānnārhā vayaṃ hantuṃ dhārtarāṣṭrānsvabāndhavān|
svajanaṃ hi kathaṃ hatvā sukhinaḥ syāma mādhava||

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