yasya nahankrto bhavo
buddhir yasya na lipyate
hatvapi sa iman lokan
na hanti na nibadhyate
One who is not motivated by false ego, whose intelligence is not entangled, though he kills men in this world, does not kill. Nor is he bound by his actions.
Commentary by Srila Prabhupada
In this verse the Lord informs Arjuna that the desire not to fight arises from false ego. Arjuna thought himself to be the doer of action, but he did not consider the supreme sanction within and without. If one does not know that a supersanction is there, why should he act? But one who knows the instruments of work, himself as the worker, and the Supreme Lord as the supreme sanctioner is perfect in doing everything. Such a person is never in illusion. Personal activity and responsibility arise from false ego and godlessness, or a lack of Krishna consciousness. Anyone who is acting in Krishna consciousness under the direction of the Supersoul or the Supreme Personality of Godhead, even though killing, does not kill. Nor is he ever affected by the reaction of such killing. When a soldier kills under the command of a superior officer, he is not subject to be judged. But if a soldier kills on his own personal account, then he is certainly judged by a court of law.
Commentary by Sri Visvanatha Cakravarti Thakur
Who then is intelligent with good eyes? One who does not have the nature of ahankara (ahankrto bhavah), who is not thinking himself the doer, who is not attached to actions by thinking the action will give good or bad results (yasya buddhir na lipyate), does not obtain reactions of karma. What else can be said? Though he may do pious or sinful acts, he does not do them. Though it may appear from ordinary vision that he has killed all these living beings, he does not kill, from his own vision, because he has no motive for the action. Therefore he is not bound. He does not receive the reactions of karma.