"I wish your horses swift and sure of foot" (III . I)
Macbeth is appearing to Banquo that he wishes him well so Banquo doesn't become suspicious.
"He [Banquo] hath a wisdom that doth guide his valor... There is none but he" (III.I)
Macbeth is becoming fearful of Banquo and it is leading him to become determined to get rid of him, for good.
"We have scotched the snake, not killed it" (III. II)
Now, Macbeth is the source behind the evil rather than Lady Macbeth. All Macbeth worries about is maintaining his power.
"Why do you keep alone, of sorriest fancies your companions making" (III . II)
"Take any shape but that," (III . IV)
Macbeth sees Banquo's ghost and is terrified by it. It shows how scared he is to lose his power.
Analysis: Macbeth's starts to take evil into his own hands during this chapter. Rather than being pressured by Lady Macbeth, he is becoming determined to maintain his power. His ambition leads to him killing Banquo because he feels Banquo and his kids are legitimate threats to stealing the throne from Macbeth. Even after Banquo is dead, he comes back in ghost form and still terrified Macbeth.