What should a wife do if her husband threatens to divorce her because she did not commit something unlawful?

There is no obedience to a creature in disobedience to the Creator. Therefore, if a husband threatens his wife with an unlawful act, she should advise him and clarify its prohibition with evidence. She must refrain from committing the unlawful act because obedience to Allah takes precedence. She should strive and resort to Allah through supplication for her husband's guidance. She can also seek help from books, tapes, or from students of knowledge or the imam of the mosque to advise her husband and remind him of Allah.