Banquo and Macbeth are both surprised to hear the witches’ predictions, but Macbeth is tempted and Banquo is disturbed.
At first, both Macbeth and Banquo both seem to joke about the witches’ suggestions that Macbeth will be king and Banquo’s sons will be king. Macbeth takes the event and writes to his wife about it, and it becomes his whole driving force, such that he declares that he has to step over the princes to be king if that’s what it takes.
Banquo asks Macbeth how he feels about the witches later on, and Macbeth lies and says he has not thought about them. Banquo realizes after Duncan dies that it was Macbeth who killed him.
Thou hast it now: King, Cawdor, Glamis, all,
As the weird women promised, and I fear
Thou play'dst most foully for't: (Act 3, Scene 1, enotes etext p. 40)
Eventually, Macbeth realizes that Banquo knows a little too much, and he has him killed. The guilt is too much for him, and he imagines the ghost of Banquo at his banquet. This foreshadows the mental trouble that Macbeth has as a result of the witches.
macbeth was thrilled by their prophecy while banqo approached it with suspicion.