Hadithcore
Sahih Muslim, 1437 b
sahih

Abu Sirma al-Khudri (Allah he pleased with him ) reported Allah's Messen- ger (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.

وَحَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، وَأَبُو كُرَيْبٍ قَالاَ حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ عُمَرَ، بْنِ حَمْزَةَ عَنْ عَبْدِ الرَّحْمَنِ بْنِ سَعْدٍ، قَالَ سَمِعْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّ مِنْ أَعْظَمِ الأَمَانَةِ عِنْدَ اللَّهِ يَوْمَ الْقِيَامَةِ الرَّجُلَ يُفْضِي إِلَى امْرَأَتِهِ وَتُفْضِي إِلَيْهِ ثُمَّ يَنْشُرُ سِرَّهَا ‏"‏ ‏.‏ وَقَالَ ابْنُ نُمَيْرٍ ‏"‏ إِنَّ أَعْظَمَ ‏"‏ ‏.‏

References2 variants
In-Book Reference
Book 16, Hadith 145
USC-MSA web (English) reference
Book 8, Hadith 3370 (deprecated numbering scheme)