Act 3: Ambition

(3.1.116-119) So is he mine, and in such bloody distance
That every minute of his being thrusts. Against my near'st of life. And though I could
With barefaced power swep him from my sight
and bid my will avouch it, yet I must not,
for certain friends that are both his and mine,
whose loves I may not drop, but wail his fall
Who I myself struck down. And thence it is, that I to your assistance do make love,
Masking the business from the common eye
For sundry weighty reasons.
-Macbeth

Macbeth is very ambitious in Act 3, scene 3. His drive to kill Banquo grows stronger because he is fearful of Banquo's noble qualities.

(3.4.119-122) Lady Macbeth: I pray you, speak not: he grows worse and worse; Question enrages him: at once, good night. Stand not upon the order of your going, But go at once.

Lady Macbeth is ambitious in the fact that she wants Macbeth to stay quiet. If he keeps talking about Banquo’s ghost, their cover will be blown.