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Macbeth:
Stay, you imperfect speakers, tell me more:
By Sinel's death I know I am Thane of Glamis;
But how of Cawdor? The Thane of Cawdor lives,
A prosperous gentlemen; and to be king
Stands not within the prospect of belief,
No more than to be Cawdor. Say from whence
You owe this strange intelligence? Or why
Upon this blasted heath you stop our way
With such prophetic greeting? Speak I charge you.
1.3.71-79

This is right after the three witches have explained that he will be Thane of Cawdor and king. Upon first hearing these predictions he thinks it to be preposterous that this would happen and is very modest claiming he would never be king. In the beginning of the play he contemplates how being king would be great, but doesn't seem like a possibility. He doesn't believe the witches at first and it takes him a while to trust them until he sees some proof of their prophecy. He has been granted a great title by the king and is content with that, for now.