I love a lot of ancient literature, but there's a special place in my heart for Oedipus Rex, or Oedipus the King. Some may know of the Oedipus Complex, old Sigmund's idea that a boy will grow up learning male behavior from his father, until he figuratively slays the father and supplants his father and marries the Mother figure. Unlike some of Sigmund's other ideas, this one isn't a just true, it's axiomatic.
But, back to Oedipus the King. The story is, in my opinion, not about Oedipus marrying his mother, but whether a man has free will or whether his fate is predetermined.
In the story, Laius is warned by the Oracle at Delphi that his son will slay him. So, he asks his wife to kill their son, but the wife passes the job off to a servant who instead gives Oedipus away.
Later, Oedipus is told by the Oracle that he will marry his mother. Thinking he is the son of the local king, he heads out, confronts his true father and kills him. Then, he dispatches the sphinx that is plaguing the kingdom and wins the hand of the former King's wife, his own mother.
Both Laius and Oedipus suffer the very fate they tried to avoid. Lesson? Don't tempt fate by trying to avoid yours.
Or, never trust an Oracle.