Why was Macbeth afraid of Banquo?

Macbeth’s fear of Banquo stems from the witches’ prophecies in Act I, Scene 3.  Of course, Macbeth is originally enraptured by the witches’ startling predictions that he will become Thane of Cawdor and King. However, when Banquo inquires about his destiny, the witches’ three-line response slowly destabilizes Macbeth and leads him to murder his former confidant and best friend.

The first witch tells Banquo that he will be “lesser than Macbeth but greater” (1.7.66). The...

Macbeth’s fear of Banquo stems from the witches’ prophecies in Act I, Scene 3.  Of course, Macbeth is originally enraptured by the witches’ startling predictions that he will become Thane of Cawdor and King. However, when Banquo inquires about his destiny, the witches’ three-line response slowly destabilizes Macbeth and leads him to murder his former confidant and best friend.

The first witch tells Banquo that he will be “lesser than Macbeth but greater” (1.7.66). The second witch tells him that he will be “Not so happy, yet much happier” (1.7. 67). Finally, the third witch tells him that “Thou shalt get kings, but thou shall be none” (1.7.68). This final line means that while Banquo himself will not be king, his sons will rule. Consequently, Macbeth agonizes over the fact that he killed Duncan and consigned himself to hell only to see Banquo’s children take control of the throne. He worries that Banquo and his son Fleance will pose a grave threat to his power and life. In fact, the threat of Banquo’s children continues to haunt Macbeth even after Banquo’s death; in Act IV, Scene I, the witches show Macbeth a line of kings followed by Banquo’s ghost. This is a clear sign to Macbeth that Banquo’s children will form a dynasty.

In fact, one could even argue that Macbeth is not afraid of Banquo; Macbeth is terrified of Banquo’s children.