What does Juliet's father tell Paris about her age when he asks to marry her?

The scene that your question targets is Act 1, Scene 2.  Paris has come to Capulet to seek Juliet's hand in marriage.  Capulet is not opposed to the idea at all.  In fact, he is in favor of Paris marrying his daughter.  He thinks it is a good match, but he asks Paris to wait two more years.  Capulet says that Juliet is a stranger to the world, which means she is still very young.  Then he tells Paris (and the audience) that Juliet is only 14 years old.  He asks Paris to wait.  

My child is yet a stranger in the world;
She hath not seen the change of fourteen years,
Let two more summers wither in their pride,
Ere we may think her ripe to be a bride.

Paris isn't exactly thrilled with the answer.  Capulet continues with extra stipulations to Paris.  Capulet tells Paris that he must woo Juliet, because Capulet's consent to the marriage is only part of the deal.  Juliet must also want to marry Paris.  

But woo her, gentle Paris, get her heart,
My will to her consent is but a part;
An she agree, within her scope of choice
Lies my consent and fair according voice.