יהושע, פרק כ׳, פסוק ה׳

A city of refuge serves a highly practical purpose, offering an absolute shield for someone who has taken a life by accident. When the blood avenger, a close relative of the deceased seeking to avenge the death, tracks the killer to the city, the local residents bear a strict obligation to step in and protect the fugitive [מצודת דוד]. They must actively assist the killer and are forbidden from surrendering him into the hands of the avenger [מצודת ציון]. This guaranteed safety is the very foundation of the refuge system, ensuring that the individual remains secure and completely protected from harm [ביאור שטיינזלץ].

However, this profound level of communal protection comes with a fundamental condition: the tragic event must have occurred entirely by mistake. The requirement that there was no prior hatred between the two parties serves to prevent a calculated crime. It ensures that a killer cannot act with cunning, masking a premeditated murder fueled by hostility as a mere accident [מצודת דוד]. To verify this, the relationship between the two individuals is examined by looking at their past interactions to confirm that no hostility existed before the fatal encounter [מצודת ציון].