Why does Macbeth seek the witches again in Act 3?

In Act Three, Scene 4, Macbeth sees the ghost of Banquo in the middle of a feast. Macbeth is startled and begins to speak to the ghost. After the feast is over, Macbeth has a conversation with his wife about the hallucination then informs her that he has a paid spy in each of the noblemen's homes. He then tells Lady Macbeth that he will go visit the three witches tomorrow because he wants to know more about his future. Macbeth is especially concerned about his safety and wants the witches to give him further information about what is next to come. In Act Four, Scene 1, Macbeth visits the three witches who summon three spirits that reveal the future. The first apparition tells Macbeth to beware of Macduff, the second spirit tells him to laugh at the power of other men because nobody born of a woman can harm him, and the third apparition says that he will not be defeated until Birnam Wood marches towards Dunsinane Hill.