What convinces Macbeth that the Witches’ prophecy is true?

Explanation:

Macbeth is convinced that the Witches’ prophecy is true when he witnesses the first part of it coming to fruition: the Thane of Cawdor, whom the Witches proclaimed would succeed, is indeed executed and Macbeth is given his title. This tangible proof, coupled with his burgeoning ambition, leads Macbeth to believe in the Witches’ supernatural powers and their ability to foretell the future, solidifying his conviction in their prophecy.