It was a provision for an accidental manslayer to go to one of the six cities of refuge in order to excape the wrath or revenge of an avenger of the deceased. He would have to plead his case and prove his innocence first before he would be able to be received into the city. A person who committed murder purposely by lying in wait for someone could not benefit from this provision. The accidental manslayer was under the protection as long as he remained in the city for the rest of his life, or until the death of the high priest. As long as he abided by this procedure, his safety could be guaranteed.
Answer by 69humblepie at 11:36 PM on Oct. 17, 2010