Shakespeare's Macbeth, need help with a quotation.?

Lady Macbeth wants to encourage him to commit the murder so she calls him a coward. To drive home the point, she says that cowardice is letting reticence (I dare not) cause a delay to (wait upon) bold action (I would). Of course, "I dare not" is actually Macbeth's conscience and his ignoring it is the downfall of both of them.