How we cite our quotes:
MACBETH Bring forth men-children only, For thy undaunted mettle should compose Nothing but males. (1.7.6)
Macbeth tells his wife that she's manly enough to only give birth to male-children. Sorry, Macbeth, but you're the one responsible for the Y-chromosome. But this is an interesting look at Early Modern ideas about gender: "masculinity" and "femininity" seem to be more about behavior than any particularly sex characteristics.
MACDUFF O gentle lady, 'Tis not for you to hear what I can speak: The repetition in a woman's ear Would murder as it fell. (2.3.12)
LOL, Macduff. He's so tied to a notion of female gentleness that he can't believe Lady Macbeth could even hear about murder, much less plot one. See, guys? Sexism hurts everyone.
LADY MACBETH Are you a man? […] O proper stuff! This is the very painting of your fear; This is the air-drawn dagger which you said Led you to Duncan. O, these flaws and starts, Impostors to true fear, would well become A woman's story at a winter's fire, Authorized by her grandam. Shame itself! Why do you make such faces? When all's done, You look but on a stool. (3.4.59)
In other words, Lady Macbeth is (yet again) telling Macbeth that he's acting like a girl—or, in this case, an old women. Honestly, we're a little surprised that—since this is Shakespeare and all —he didn't just up and kill her instead of Duncan.