'Avenger of Blood' in the Bible

that the slayer that killeth any person unawares and unwittingly, may flee thither. And those cities shall be your refuge from the avenger of blood.

And when the avenger of blood followeth after him they shall not deliver the slayer unto his hand: because he smote his friend ignorantly, and hated him not before time.

These were the cities appointed for all the children of Israel, and to the strangers that Sojourned among them that whosoever killed any person ignorantly, the same might flee thither and should not die by the hand of the avenger of blood, until he stood before the congregation.