It was narrated from Safiyyah bint Abi 'Ubaid from one of the wives of the Prophet, and from Umm Salamah, that the Prophet said:"It is not permissible for a woman who believes in Allah and the Last Day to mourn for anyone who dies for more than three days except for a husband; she should mourn for him for four months and ten (days)

English translation · Sunan an-Nasa'i