How can one who knows this indwelling presence as indestructible, eternal, unborn and inexhaustible ever kill another or cause another to kill?
The solution Arjuna needs to redress his grief, doubt and constriction is not physical, like abandoning the war and becoming a mendicant. He should gain true spiritual wisdom about the lasting presence in the body. That alone will remove all causes for agitation and delusion.
Knowledge is the real goal of human life. Know the ‘I’ to be indestructible, eternal, unborn, irreducible. Then the thought of one killing another, and the other getting killed, does not arise. How can the Self-Knower be killing anyone or causing another to kill? Krishna is stating a fact, not inciting Arjuna to kill!
Stripped of war context, it means ‘how can one act, or cause another to act’. No action can befall the Self. Actions are in the sensory, oral, mental and intellectual levels, and rest on these instruments alone. Nothing touches and involves the Self!