Please give quotes that show how Macbeth is ambitious and how his mind unfolds into murderous intentions towards King Duncan.

Sparklekid has the most important quote in the answer
given previous.  In Act I, scene vii comes a very famous soliloquy in the play.  I would
say that there are random quotes peppered throughout the scenes that lead up to this
soliloquy, but this is the first moment that Macbeth is onstage alone to confide his
inmost thoughts to the audience.  The whole of the speech is the "unfolding" of "his
mind" "into murderous intentions towards King Duncan."  He
says:

If it
were done when 'tis done, then 'twere well

It were done
quickly; if the assassination

Could trammel up the
consequence, and catch

With his surcease success; that, but
this blow

Might be the be-all and end-all
here,

But here, upon this bank and shoal of
time,

We'ld jump the life to
come.

In these opening lines
of the speech, Macbeth admits that, if he could murder Duncan and be assured of no
consequences for his action, he would do it without pause.  But, he knows that the world
does not work this way.  He continues:

readability="14">

. . .But in these
cases

We still have judgement here:  that we but
teach

Bloody instructions, which, being taught,
return

To plague the inventor.  This even-handed
justice

Commends the ingredients of our poison'd
chalice

To our own
lips.

So, for Macbeth, the
idea of karmic retribution, or the idea of his evil deeds coming home to roost, is a
potential reason not to go forward with the murder.  He goes on in the speech to list
other reasons, but, as good and sound and true as his reasoning is, he ignores it all in
favor of his ambition:

readability="9">

. . .I have no
spur

To prick the sides of my intent,b ut
only

Vaulting ambition, which o'erleaps
itself

And falls on the
other.

This speech is the
best single bit of text from the play that reveals the inner workings of Macbeth's mind,
rather than a simple reaction to outside circumstance or another character's words or
actions.  He speaks this soliloquy alone onstage to only the audience, and it is in this
speech that the audience sees the reasoning Macbeth undergoes in deciding to kill
Duncan.

Please follow the links below for further analysis
of this speech.