* The witches call Macbeth "fair is foul, and foul is fair" (l. 12) as he approaches them. This is the first instance of the motif in the play.
* Macbeth and Banquo discuss the witches and their prophecies. Macbeth is excited about the possibility that he may become king, but he is also worried about the consequences of their actions. Banquo is more cautious and warns Macbeth that he should not be too quick to believe the witches.
Act III, Scene i
* Macbeth has become king of Scotland, but he is not happy. He is haunted by guilt and fear. He begins to see Banquo as a threat and orders him to be killed.
* Macbeth meets the witches again and they give him more prophecies. They tell him that he will be defeated by a man who is not of woman born and that he will be safe until the Birnam Wood comes to Dunsinane Hill.
These events show how the motif of fair is foul, foul is fair is used throughout the play to explore the themes of ambition, guilt, and madness. Macbeth is lured by the witches' promises of power, but he is ultimately destroyed by his own ambition.