Sahih Muslim Book 8, Hadith Number 3370.

Chapter: It is forbidden to divulge the secret of the woman.

Abu Sirma al-Khudri (Allah he pleased with him) reported Allah’s Messenger (May peace be upon him) as saying: The most important of the trusts in the sight of Allah on the Day of judgment is that a man goes to his wife and she goes to him (and the breach of this trust is) that he should divulge her secret Ibn Numair narrates this hadith with a slight change of wording.