In this soliloquy from Act 2, Scene 1, of Macbeth, personification is used to show how Macbeth thinks that natural and supernatural forces are acting on, against, or for him. At the beginning of the soliloquy, Macbeth debates on whether he's hallucinating or seeing a real dagger. Then he proceeds to debate on role of supernatural influence on his thoughts. And this leads him to personify things such as murder, dreams, and witchcraft as if they were actual people capable of influencing him.
As the world sleeps, "nature seems dead," and this comparison between sleep and death is a manifestation of Macbeth's as he considers murdering Duncan in his sleep. Here, nature is personified but nature can also mean life.
Macbeth says that "wicked dreams abuse" people (including himself) in their sleep. He is personifying dreams but also making a reference to the supernatural. Thus, a link is established between people's dreams and the supernatural. In Macbeth's case, one of his dreams is to be king and this has been suggested by the supernatural witches. Given that he's personified dreams, it creates an ambiguity: are his "wicked" dreams of his own making or is he really at the mercy of the influence of the witches? This is one of the debates about the play: to what extent is Macbeth tricked, guided by Fate, or are these wicked dreams products of his own twisted free will?
Macbeth, with his wife, has celebrated the prophecies the witches have told him. But he passes the blame, saying that witchcraft celebrates these offerings. Witchcraft can mean the actual work of witches or a personified abstract witchcraft as a force of evil.
In lines 60-64, Macbeth again combines his motives with the motives of an abstract: Murder. Here, Murder is personified as if Macbeth believes he might be under the guidance of the personified Murder which is directed by supernatural forces.
In the next lines, Macbeth asks that his steps not be heard so that he, like Murder, can move "like a ghost." All of these personifications raise the intensity because Macbeth is conflating his motives with the will of supernatural forces. Another way to think about it is that Macbeth, especially in this last example, is psyching himself up, trying to become like Murder.
This last example also echoes Lady Macbeth's speech in Act 1, Scene 5, when she asks the supernatural to change her so that she will be able to help her husband carry out the murders.
Come, you spirits
That tend on mortal thoughts, unsex me here
And fill me, from the crown to the toe, top-full
Of direst cruelty! (I.v.41-44)