במדבר, פרק ל״ה, פסוק כ״ז

A person who accidentally kills another finds safety within the walls of a city of refuge. As long as he remains inside, he is protected, but stepping outside those borders completely strips away his legal protection and puts his life at risk. If the accidental killer wanders outside the city, the closest relative of the victim—known as the blood avenger—has the right to strike him down. However, taking the killer's life is not an absolute obligation; it is simply a permitted choice placed in the hands of the avenger [הכתב והקבלה, תורה תמימה].

The law makes a subtle distinction regarding who exactly may carry out this act. The primary focus is on the actual relative of the victim, for whom avenging the death is seen as fulfilling a duty. Yet, the concept of the avenger is also broadened to include any individual who takes it upon themselves to seek justice for the victim. For an unrelated person acting in this role, killing the accidental murderer is not a duty but merely a permitted act [מלבי״ם].

A key question arises regarding the legal guilt of whoever kills the accidental murderer outside the city limits. One perspective suggests that the avenger is completely clear of any guilt and faces no punishment for the bloodshed [ביאור שטיינזלץ]. However, the primary approach among commentators is that the legal focus is actually on the accidental killer himself. The moment he steps outside the city of refuge, he is legally viewed as a dead man. Striking him down is equated to striking a lifeless body [רש״י, שד״ל, הכתב והקבלה].

This perspective leads to an important legal distinction for anyone other than the official blood avenger. While the designated avenger has the explicit right to harm the killer, an ordinary person is initially forbidden from doing so. Nevertheless, if a stranger does go ahead and kill the accidental murderer outside the city, that stranger is exempt from punishment. Because the killer had already lost his legal right to life by leaving his sanctuary, the stranger is viewed as having struck a person who was already considered dead [הכתב והקבלה, תורה תמימה].