And Zainab narrated that after that I came to Zainab bint Jahsh (may Allah be pleased with her) when her brother had passed away, so she called for perfume and applied it, then said: "By Allah! I had no desire for perfume, but I heard the Messenger of Allah (ﷺ) say from the pulpit that it is not permissible for any woman who believes in Allah and the Last Day to mourn for any deceased person for more than three days, except for her husband, for whom the mourning period is four months and ten days."
Hadith Referenceمسند الإمام الشافعي / كتاب العدد والسكنى والنفقات / 1310
Hadith Takhrijاخرجه البخاري، الطلاق، باب تحد المتوفى عنها اربعة اشهر وعشرا (5335) ومسلم، الطلاق، باب وجوب الاحداد في عدة الوفاة .... الخ (1487)۔