Shakespeare was such a gifted writer that all of his plays seem to offer a wide array of quotations of dramatic significance. In Macbeth, some of these quotes are found in Macbeth's soliloquies (actor's speech to self or the audience).
Examples of some of Macbeth's more popular quotations are in his "Is this a dagger I see before me…" speech, found in Act Two, scene one, beginning at line 33. It is in this scene that Macbeth is on his way to kill his King and friend, Duncan, and he sees the image of a dagger hovering in front of him, almost leading on his way to Duncan's room.
There is also his "Tomorrow, And Tomorrow" speech at the end of the play in Act Five, scene five, lines 17-28. This is the speech that Macbeth delivers when he discovers that his wife has killed herself. He is beginning to tire of the life he has chosen for himself, as seen in his comment that Lady Macbeth would have died at some point.
The previous quotes are of dramatic significance.
There are other quotes that are perhaps not as often quoted, but are still familiar to students of Shakespeare, and also offer dramatic significance. The following quote is found in Act One. It speaks of the Thane of Cawdor and how bravely he goes to his death—dying more nobly than he lived:
Nothing in his life
became him like the leaving of it. (I.iv.7-8)
This quote is delivered by Malcolm to his father, Duncan, regarding how valiantly the Thane of Cawdor—traitor to the Scottish crown— went to his execution. (This scene also foreshadows the end of the play, in the death of Macbeth—the new Thane of Cawdor, also a traitor.)
Another significant quote is delivered by the Doctor in Act Five, speaking of Lady Macbeth's sleepwalking (and "talking") malady. However, it is an important theme with regard to who the best healer is for one whose heart and/or conscience is ailing:
The patient must minister to himself. (V.iii.45-46)
The Doctor reports that if Lady Macbeth is to get well, she needs to do it herself. He doesn't have any medicine that will heal her heart of her deep sadness and guilt. This could also apply to Macbeth who has destroyed himself for the love of the crown—not the love of his country. The statement is almost prophetic in that the Doctor says what must be done, but we get the sense that Lady Macbeth—the determined and frightening instigator of Duncan's murder—has gone beyond a place where she change her situation, inferring that no healing is possible.
The previous quote is also reminiscent of the biblical verse found in Luke 4:23 found below.
Physician, heal thyself.