Read the opening scene prior to macbeth's entrance what do you think is the purpose of this scene

The purpose of this scene in Macbeth is that Shakespeare's Macbeth is a tragedy in which one man rises to a high position then falls, a series of events some blame either on the witches or fate.  The opening of scene 1 act 4 refers to a picture of how even a villainous traitor can die with dignity.

Well where is the passage!