Numbers 35:16
And if he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death. And if he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death.
The verse belongs to the appointment of six cities of refuge among God's people of old, which tempered the custom by which the next of kin of a murdered person avenged the death by killing the killer. Striking a person with an instrument of iron so that he dies is murder, and the murderer shall surely be put to death. That law distinguishes willful, intentional, premeditated murder from accidental, unintentional killing.
Only the accidental slayer may find protection in a city of refuge, for the cities protected only those who killed accidentally. The slayer who had caused a death could flee there to escape and receive a fair trial before the congregation, with protection from private vengeance until judgment. Elders were able to admit a fugitive while a full trial was arranged, and the circumstances were considered — including hatred, lying in wait, and acting presumptuously or deceitfully — before a guilty murderer was delivered up for punishment. An accidental killer is not punished, while a guilty murderer does not escape legal consequences.
A convicted murderer cannot buy freedom with money and no ransom is permitted, and rich and poor are to be judged without favoritism. Executing a convicted murderer is the penalty for violating the sixth commandment, not a violation of it, and it restrains further murder. The fugitive must flee to and dwell inside the city of refuge until the death of the high priest, and leaving before then forfeits protection and exposes him to the avenger of blood and to judgment.
The provision offered mercy and escape from death to the unintentional transgressor, but it did not excuse continued wrongdoing. The appointed cities were true cities of safety, safer than the strongly fortified cities of the world that are thought to give safety but still fall. The cities typify Christ and the avenger of blood typifies God's law relentlessly pursuing the sinner and demanding his life; the sinner who flees to Christ is safe and the law is satisfied. Since Christ as priest after the order of Melchisedec dies no more but lives forever to make intercession, the one abiding in him is eternally safe and saved to the uttermost, while believers are safe from wrath in him but those who depart from him face destruction.