Today's reading is Numbers 35-36 (read it in the KJV or NIV)
Today's passage covers the commandment to give Canaanite towns to the Levites; the laws regarding cities of refuge; and the continuation of the case of Zelophehad's daughters' inheritance.
It was bound to happen sooner or later. You're up on your ladder one day, adding some stones to your silo, when you accidentally drop one. Bad luck! Someone wasn't paying attention to the old proverb about not walking under ladders and thump! The rock landed right on his head and killed him. You had no ill will for this man; maybe you never even met him before. But he's dead all the same, and his family is going to send their avenger of blood after you. What do you do?
If you're an ancient Israelite living after the conquest of Canaan, you decide that discretion is the better part of valour and run away. Specifically, you run away to one of the six cities of refuge, which provide specifically for cases like yours.
Perhaps some backtracking is in order.
In Num. 35, God commands the Israelites to set aside forty-eight cities and their suburbs for Levite use. (Num. 35:1-8) These cities are to be scattered throughout the Israelite lands. Among them, God specifically says to appoint six of these forty-eight cities to act as "cities of refuge," where people guilty of manslaughter may hide from "avengers of blood" while awaiting trial. (Num. 35:9-15) These six cities will be split, three on the main, Western side of the Jordan river, and three on the trans-Jordan, Eastern side.
The procedure, according to the text (Num. 35:16-28), worked as follows: if a man was guilty of manslaughter, he had permission to flee to one of the six cities of refuge. There, he would await trial by "the congregation," who would judge between him and the avenger of blood. If he is found guilty of murder, he must be killed. If, however, he is only found guilty of manslaughter, he is allowed to stay in the city of refuge, safe from the avenger of blood. In fact, he must stay in the city of refuge until the death of the high priest. After that, he is allowed to return to his own property. If he leaves before the high priest dies, his can be killed by the avenger of blood without penalty to the latter.
Some people might point out a few flaws in this system. First, how to we know who is guilty of manslaughter, as opposed to murder? Thankfully, at least in this case, the text helps us. Num. 35:16-23 provides the distinction. Murder is when someone kills another by striking him with an iron object, a stone, a wooden object, or with malice aforethought or hostility. Manslaughter occurs when the strike (barehanded or with a stone) is accidental, unintentional, and without hostility. Obviously, the lines between these two categories can become blurred, especially when it comes to intent and motivation. Hence the necessity to have a trial to hear both sides of the case, the killer's and the avenger's.
The next problem is the time limit involved. The position of high priest was at least somewhat hereditary, given over to Aaron's descendants. Unlike the modern system of papal election, which almost by necessity elects an elderly person to the office of pope, an Israelite high priest might be relatively young. Assuming the office was passed from father to son, a son might have twenty, thirty, or more years of service as high priest before passing it along to his son. This is, understandably, quite a long time for someone to wait in a city of refuge, far from his lands and his family. This might be the reason for the clause saying that anyone who leaves the city of refuge early is at the mercy of the avenger of blood. (Num. 35:26-28) Not everyone would have the mental stamina to remain in a city of refuge if the high priest was relatively young and showed no signs of premature death.
Finally, we must point to the avenger of blood himself. Ancient Israelite culture is far from the only one to contain this concept. The idea is that one of the victim's family members is allowed to avenge his slain kinsman, generally by killing the murderer. The obvious pitfall to this method is one of escalation. I kill your brother; you kill me; my brother kills you; and so forth. In some cultures, such as the medieval Saxons and Franks, this could escalate into full-scale feud. Many cultures included some built-in method to stem the tide of blood before it became a river. The Franks, for example, allowed the murderer to pay the victim's family in compensation. The ancient Israelites, on the other hand, set clear boundaries for when and where an avenger of death was allowed to engage in vendetta: cases of murder as judged by the congregation, or cases of manslaughter when the perpetrator left the city of refuge before the death of the high priest.
In short, this seems at least in theory to be a workable system. To return to our original example, of our poor stone-mason who accidentally finds himself with blood on his hands, we could offer him this advice: run to the nearest city of refuge, hope that the congregation judges that this was a case of manslaughter, and stay there. And don't worry about your next harvest; if you go go home to finish your silo, you might find yourself dead before you get there.