"Ευμενίδες" by Aeschylus is a tragedy written in ancient Greece as the final play of the Oresteia trilogy. After killing his mother Clytemnestra, Orestes flees to Delphi pursued by the vengeful Furies. When he seeks refuge in Athens, the goddess Athena establishes a trial to judge his crime, creating the first court of law. The conflict between ancient blood vengeance and civilized justice reaches its climax as gods and mortals debate guilt, punishment, and the transformation of rage into mercy.
Wikipedia page about this book: el.wikipedia.org/wiki/%CE%95%CF%85%CE%BC%CE%B5%CE%BD%CE%AF%CE%B4%CE%B5%CF%82_(%CE%91%CE%B9%CF%83%CF%87%CF%8D%CE%BB%CE%BF%CF%85))