What lines in the play Macbeth portray ambition?

The two characters that  display the most ambition in this play
are Macbeth himself and Lady Macbeth.  They reveal the depth of their ambition in their
willingness to murder Duncan in order for Macbeth to gain the throne, as predicted by the Weird
Sisters.

They each confess their ambition to the audience -- Lady
Macbeth in Act I, scene v, and Macbeth in Act I, scene vii.

Lady
Macbeth receives a letter from Macbeth, telling her of the witches' predictions.  Immediately,
her ambition is inflamed.  She says:

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Glamis thou art and Cawdor; and shalt
be

What thou art promised. .
.

And
later:

The raven
himself is hoarse

That croaks the fatal entrance of
Duncan

Under my
battlements.

By determining that
Macbeth "shalt be" King (what he was promised by the witches) and calling Duncan's entrance into
Macbeth's castle "fatal," Lady Macbeth shows how readily she embraces any action necessary in
order to make her husband King.

Two scenes later, Macbeth reveals
that he is motivated by the same ambition as Lady Macbeth.  In his first soliloquy of the play,
he reveals to the audience that, though there are numerous reasons that killing Duncan is a
really bad idea, he will go forward with the plan anyway.  His reason?  Ambition.  He
says:

. . .I have no
spur

To prick the sides of my intent, but
only

Vaulting ambition. .
.

And so, both Lady Macbeth and
Macbeth, by the end of Act I, have committed to a treasonous course of action:  the killing of
King Duncan in the name of ambition.