The answer is: Accidental murder

Josh 20:3

Cities of refuge, as noted in Joshua 20:3, served a critical purpose in ancient Israelian law—they were safe havens for individuals who caused accidental deaths. This concept springs from a deep understanding of justice, where a person who committed an unintentional homicide could flee from retribution and receive a fair trial, rather than meting out instant vengeance.

Interestingly, the idea of juxtaposed justice can be seen in many cultures throughout history. For instance, ancient Roman law also recognized the importance of intent, suggesting a universal acknowledgment that while the outcome of an action is significant, a person's intent must be taken into account for moral and legal judgments. This resonates with the modern legal principle of “mens rea,” or the intention behind an act.

Now, if you're familiar with the traditionally numbered six cities of refuge—Kedesh, Shechem, Hebron, Bezer, Ramoth, and Golan—you might find it interesting to note that they represent the grace of opportunity in a time when retribution could easily spiral into blood feuds. This kindly retrofitting of justice reflects a phase where it focused on fairness whether that benefits a perpetrator or a victim’s kin.

Furthermore, the cities of refuge echoed God’s compassion and mercy, offering those who strayed unintentionally a lifeline. Isn't it refreshing to think of justice wrapped in such mercy today? So much of our interactions could benefit from so much equal balance—a focus both on accountability and the context behind our actions.