Bhagavad Gita
2.19

य एनं वेत्ति हन्तारं यश्चैनं मन्यते हतम् | उभौ तौ न विजानीतो नायं हन्ति न हन्यते ||१९||

ya enaṁ vetti hantāraṁ yaśh chainaṁ manyate hatam ubhau tau na vijānīto nāyaṁ hanti na hanyate

Translation

He who thinks that this (soul) is a slayer and he who thinks that this (soul) is slain — both of them fail to perceive the truth. This soul neither slays nor is slain.

Interpretation

The killer and the killed are both mistaken in their identification of the soul with the body. When a soldier kills on the battlefield, he destroys a body, not a soul. When someone dies, their soul does not die. Both the conception of 'killing' and 'being killed' are based on identification with the perishable body.