Deuteronomy 19:12
Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die. Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die.
The verse belongs to the laws rehearsed to Israel before crossing the Jordan into the promised land, recalling laws God had given them and impressing the importance of keeping them. It states the law of blood revenge in a restricted form, which existed in germ in patriarchal times as Genesis 4:14-15 indicates. Its context is the case of a man who hated his neighbor, lay in wait, and killed him, showing that a deliberate killing was treated as murder, not accidental manslaughter.
A fugitive's case was decided at a city gate, a public place where judges held sessions, and the refuge gate was likely staffed day and night to receive fugitives. The elders' initial decision admitted him to the city of refuge, while a regular trial before a higher court followed after witnesses had been summoned and the accusers had time to appear. The slayer thus received a trial in the city of refuge where his case could be heard and it would be decided whether he could remain there or be handed over for punishment. The refuge protected the accused until a fair trial established guilt or innocence.
The elders were to bring a fugitive from the city of refuge before the avenger of blood only after the law's process determined his case. The provision did not let relatives exact private revenge or make the avenger the judge. When the case called for it, the elders must send and fetch him from where he has fled and deliver him into the hand of the avenger of blood, that he may die. In case of murder the stern law of life for life was carried out by the murdered man's Goel as revenger of blood, for there were no civil officers to execute the murderer; he died by the hand of the murdered man's Goel himself.