The Torah in Parashat Maseh (Bamidbar 35:25) commands that in the case of an accidental murder, the Bet Din is required to send the killer to an “Ir Miklat” – one of the designated “cities of refuge,” where he would be protected from the victim’s relatives who might seek revenge. Later (32:28), the Torah adds that the murderer must remain in the Ir Miklat until the death of the Kohen Gadol.
The Sefer Ha’hinuch explains that the reason behind this Misva relates to the unique severity of the crime of murder. One who intentionally kills, the Sefer Ha’hinuch writes, is not spared from harsh punishment regardless of how otherwise righteous he might be. Therefore, when one kills mistakenly, the fact that he ended up committing such a grave sin, albeit without intention, necessitates atonement, and so the Torah requires him to go into exile. The Sefer Ha’hinuch writes that exile is a very harsh punishment, as a person leaves his loved ones and peers, as well as his homeland, and must live among strangers. The distress of exile brings atonement for the accidental crime of murder which was committed.
Additionally, of course, this requirement serves to protect the killer, as in the Ir Miklat he finds refuge from the victim’s relatives looking to avenge their loved one’s death.
Thirdly, the Sefer Ha’hinuch writes, the Torah does not wish for the killer to live in the same community as the victim’s family members. This would, quite obviously, create a very uncomfortable situation, and cause a great deal of tension. Even if the victim’s family members are not seeking revenge, they are nevertheless embittered and resentful. As the Torah wishes to create a pleasant, comfortable atmosphere, it requires the killer to leave his town in order to avoid frequent interaction between him and the victim’s family.
The killer must exile to an Ir Miklat only if the victim died immediately when the accident occurred. If the victim survived for some time and then passed away, the killer is exempt from the obligation to relocate in a city of refuge.
If, Heaven forbid, someone accidentally killed his parent, or child, this obligation applies, and the killer must relocate in an Ir Miklat. If, however, a father accidentally killed his child while teaching the child Torah or a trade, such as if he struck the child to direct his attention to his studies, unintentionally killing the child, the parent does not go to an Ir Miklat. Since the tragedy occurred in the process of fulfilling a Misva – teaching one’s child Torah, or a profession – the obligation to go into exile does not apply.
When a person is required to exile to a city of refuge, his Rabbi who teaches him Torah must go with him. This is inferred from the Torah’s command that the killer “flee to one of these cities, and live” (Debarim 4:42). The wisdom of Torah is crucial for life, and thus the word “Va’hai” (“and live”) in this verse implies that the person must be given the opportunity to continue learning Torah when he relocates in an Ir Miklat.
If the killer died before reaching the city of refuge, his remains are brought there for burial.
The Gemara discusses at length which types of accidental murder require one to exile to an Ir Miklat, and which do not. The basic rule is that if the accident occurred through negligence, such that the killer bears a degree of responsibility, then he must go to an Ir Miklat. If the situation resembles one of “Oness” – extenuating circumstances, where the killer cannot be said to have been criminally negligent, then he is not required to go into exile. The Gemara gives the example of one who kills while climbing a ladder, which is not likely to happen, and one who kills while coming down a ladder, when greater caution is expected. In the former case, the killer cannot be said to have been criminally negligent, and is thus not required to go to a city of refuge, whereas in the latter case, he bears responsibility, and must go into exile.
If a Kohen Gadol mistakenly killed, he can go to the Bet Ha’mikdash and serve at the altar, where he is protected from the victim’s relatives as though he was in an Ir Miklat. After he finishes performing the service, he is escorted to an Ir Miklat.
This Misva applies when the Jews are living in the Land of Israel, and there is a Sanhedrin. If a Bet Din failed to send an accidental killer to relocate in an Ir Miklat in a situation where this is required, they are in violation of this affirmative command. The Sefer Ha’hinuch warns that they are liable to severe punishment, as the failure to enforce these rules results in less care and caution in society, and thus leads to the loss of life.