2.18
अन्तवन्त इमे देहा नित्यस्योक्ताः शरीरिणः | अनाशिनोऽप्रमेयस्य तस्माद्युध्यस्व भारत ||१८||
antavanta ime dehā nityasyoktāḥ śharīriṇaḥ anāśhino'prameyasya tasmād yudhyasva bhārata
Translation
Only the material body of the indestructible, immeasurable, and eternal living being is subject to destruction; therefore, fight, O descendant of Bharata!
Interpretation
The logical conclusion: since the soul is eternal and only the body perishes, there is no real 'killing' in the deepest sense. The soul cannot be slain. Therefore, the warrior's duty to protect dharma through battle is not a sin against the soul. 'Therefore fight!' — Krishna's first direct command.