Sahih Muslim 1487
Sahih Muslim · Book 18: The Book of Divorce · The Obligation to mourn during the 'Iddah following the death of one's husband, but it is forbidden to mourn for more than three days in other cases
وَحَدَّثَتْهُ زَيْنَبُ ، عَنْ أُمِّهَا ، وَعَنْ زَيْنَبَ ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَوْ عَنِ امْرَأَةٍ مِنْ بَعْضِ أَزْوَاجِ النَّبِيِّ صلى الله عليه وسلم .
This hadith was narrated by Zainab from her mother and from Zainab, the wife of Allah's Apostle (ﷺ), or from some other lady from among the wives of the Prophet (ﷺ).