'Avenger of Blood' in the Bible

That the slayer that kills any person accidentally and unintentionally may flee there: and they shall be your refuge from the avenger of blood.

And if the avenger of blood pursues after him, then they shall not deliver the slayer up into his hand; because he struck his neighbor unintentionally, and hated him not beforehand.

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