Foreshadowing appears in most scenes in Shakepeare's "Macbeth," including the very first scene with the three witches, which foreshadows the violent, unnatural events in the play with the phrase, "Fair is foul, and foul is fair." In Act I, Scene 2, when Duncan awards Macbeth the title Thane of Cawdor, which has been taken from a traitor, the origin of the title foreshadows Macbeth's eventual betrayal of the king.
At the end of Act I and the beginning of Act II, Macbeth hallucinates the daggers and thinks he hears a voice while killing Duncan, foreshadowing the insomnia and insanity that plague Macbeth and his wife for the rest of the play. In Act II, Macduff?s suspicions of Macbeth immediately after Duncan?s murder and his refusal to see Macbeth crowned foreshadow his later opposition to Macbeth.
At the beginning of Act III, Banquo's soliloquy shows that he remembers the witches' prophecy and suspects that Macbeth has killed the king to get the throne. Since Banquo knows that the witches said that his descendants would be king rather than Macbeth's descendants, this soliloquy foreshadows that Macbeth has not finished securing the throne and that Banquo is now in danger.
The final encounter with the witches makes Macbeth feel invincible. He thinks he is unconquerable, based on the prophecies that "no man born of woman" could defeat him and that his defeat wouldn't come until Birnam Wood moved to Dunsinane. But the witches have really shown Macbeth his downfall by warning him of the conquering army's battle plans and that he should "beware Macduff" because of Macduff's unusual birth.