كتاب الطلاق
18  
The Book of Divorce
(9)
Chapter: 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
(9)
باب وُجُوبِ الإِحْدَادِ فِي عِدَّةِ الْوَفَاةِ وَتَحْرِيمِهِ فِي غَيْرِ ذَلِكَ إِلاَّ ثَلاَثَةَ أَيَّامٍ
Sahih Muslim 1488 d

Humaid b. Nafi' narrated two traditions from Umm Salama dealing with collyrium and the other hadith from the wives of Allah's Prophet (ﷺ) except with this that no mention was made of Zainab.

وَحَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ حُمَيْدِ بْنِ نَافِعٍ، بِالْحَدِيثَيْنِ جَمِيعًا حَدِيثِ أُمِّ سَلَمَةَ فِي الْكُحْلِ وَحَدِيثِ أُمِّ سَلَمَةَ وَأُخْرَى مِنْ أَزْوَاجِ النَّبِيِّ صلى الله عليه وسلم غَيْرَ أَنَّهُ لَمْ تُسَمِّهَا زَيْنَبُ نَحْوَ حَدِيثِ مُحَمَّدِ بْنِ جَعْفَرٍ ‏.‏
Reference : Sahih Muslim 1488d
In-book reference : Book 18, Hadith 77
USC-MSA web (English) reference : Book 9, Hadith 3542
  (deprecated numbering scheme)