Num 35:9-15 And the LORD spoke to Moses, saying, “Speak to the people of Israel and say to them, When you cross the Jordan into the land of Canaan, then you shall select cities to be cities of refuge for you, that the manslayer who kills any person without intent may flee there. The cities shall be for you a refuge from the avenger, that the manslayer may not die until he stands before the congregation for judgment. And the cities that you give shall be your six cities of refuge. You shall give three cities beyond the Jordan, and three cities in the land of Canaan, to be cities of refuge. These six cities shall be for refuge for the people of Israel, and for the stranger and for the sojourner among them, that anyone who kills any person without intent may flee there.
Num 35:29-33 And these things shall be for a statute and rule for you throughout your generations in all your dwelling places. “If anyone kills a person, the murderer shall be put to death on the evidence of witnesses. But no person shall be put to death on the testimony of one witness. Moreover, you shall accept no ransom for the life of a murderer, who is guilty of death, but he shall be put to death. And you shall accept no ransom for him who has fled to his city of refuge, that he may return to dwell in the land before the death of the high priest. You shall not pollute the land in which you live, for blood pollutes the land, and no atonement can be made for the land for the blood that is shed in it, except by the blood of the one who shed it.
The purpose of the cities of asylum was to protect the manslayer who kills any person accidentally. They were to protect someone in the case of manslaughter as opposed to murder. In the ancient culture of Israel, it was not left entirely up to the government to avenge a murder. Each extended family had a recognized avenger who would ensure that one who murdered a family member would likewise be killed. The institution of the family avenger was never commanded in Scripture; it was a broad cultural practice that was regulated by Scripture. “It is quite possible to do unjust things in the name of justice. It was against such a possibility that these cities were provided.” Therefore, such a man could flee to a city of refuge – an appointed Levitical city, where he could stay, safe from the avenger of blood, until he could stand before the congregation in judgment and he could leave the city of refuge safely. (Guzik)
To show plainly the abhorrence of murder, and to provide the more effectually for the punishment of the murderer, the nearest relation of the deceased, under the title of avenger of blood, (or the redeemer of blood,) in notorious cases, might pursue, and execute vengeance. A distinction is made, not between sudden anger and malice aforethought, both which are the crime of murder; but between intentionally striking a man with any weapon likely to cause death, and an unintentional blow. In the latter case alone, the city of refuge afforded protection. Murder in all its forms, and under all disguises, pollutes a land.
Does not the highway of salvation, resemble the smooth and plain path to the city of refuge? Survey the path that leads to the Redeemer. Is there any stumbling-block to be found therein, except that which an evil heart of unbelief supplies for its own fall?
The gate of the city stood open night and day. Has not Christ declared, Him that cometh unto me I will in nowise cast out? 5. The city of refuge afforded support to every one who entered its walls. Those who have reached the refuge, may live by faith on Him.
The city was a refuge for all. In the gospel there is no respect of persons. That soul lives not which deserves not Divine wrath; that soul lives not which may not in simple faith hope for salvation and life eternal, through the Son of God.
(Henry)