They hail’d him father to a line of kings:
Upon my head they placed a fruitless crown,
And put a barren sceptre in my gripe,
Thence to be wrench’d with an unlineal hand,
No son of mine succeeding.
– William Shakespeare
Macbeth, Act 3, Scene 1. Macbeth is now king but he doesn’t feel secure and is afraid of Banquo, as is evident in his soliloquy. In a metaphor, Macbeth says that the Witches gave him a “barren sceptre” with their prophecy that he would be king. He describes the sceptre as barren, because the witches also said that the throne would pass to Banquo’s descendants. Macbeth is angry and his ambition is frustrated, because he doesn’t have children to pass on the throne to, and it will go to Banquo’s sons.