'Avenger' in the Bible

that the manslayer that killeth any person unwittingly and unawares may flee thither: and they shall be unto you for a refuge from the avenger of blood.

And if the avenger of blood pursue after him, then they shall not deliver up the manslayer into his hand; because he smote his neighbor unawares, and hated him not beforetime.

These were the appointed cities for all the children of Israel, and for the stranger that sojourneth among them, that whosoever killeth any person unwittingly might flee thither, and not die by the hand of the avenger of blood, until he stood before the congregation.