Abu Sa'id al-Khudri (RA) reported Allah's Messenger (ﷺ) 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.
Related hadith on this topic
Explanation & Benefits
Shaykh Maulana Abdul Aziz Alvi
Hadith Commentary: Benefits and Issues: A husband and wife have intercourse with each other in seclusion from people, which is an indication that this is a concealed act, the disclosure of which is not appropriate. Therefore, if a husband and wife describe or depict this act and its details before others, it is a betrayal of trust and the disclosure of a hidden secret, which is an extremely reprehensible act and one that is liable to accountability.
Source: Tuhfat al-Muslim: Commentary on Sahih Muslim, Page: 3543
Shaykh Umar Farooq Saeedi
Benefits and Issues:
Allah, the Mighty and Majestic, has made husband and wife as garments for one another, so to disclose each other's secrets before others is a very reprehensible act.
Except in the case where, due to some Shar‘i necessity, one is required to mention something before a judge (qadi) or the like.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 4870