Deuteronomy 19:6, 12

lest the avenger of blood, while his anger is hot, pursue the manslayer and overtake him, because the way is long, and kill him, though he was not deserving of death, since he had not hated the victim in time past.

then the elders of his city shall send and bring him from there, and deliver him over to the hand of the avenger of blood, that he may die.