Lord Capulet says, "I tell thee what: get thee to church o' Thursday,
Or never after look me in the face.
Speak not. Reply not. Do not answer me."
He tells Juliet that if she does not get to church on Thursday that she is never to see him or speak to him again. He is basically telling her that if she does not marry Paris, he will disown her. During this time period this would most likely feel like a death sentence to a girl Juliet's age. Women of her rank and standing did not have anywhere to go or anyone to look after them if they were exiled from their families.
