Narrated by Aisha and Hafsa (may Allah be pleased with them): The Messenger of Allah (ﷺ) said: "It is not permissible for a 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 / 1312
Hadith Takhrijاخرجه مسلم ،الطلاق، باب وجوب الإحداد فى عدة الوفاة وتحريمه في غير ذلك الا ثلاثة ايام (1490) ، (1841)۔