'Avenger of Blood' in the Bible

lest the avenger of blood pursue the manslayer, while his heart is hot, and overtake him, because the way is long, and strike him mortally; whereas he was not worthy of death, inasmuch as he didn't hate him in time past.

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