Sunan An-Nasa'i

It was narrated that Zainab bint Umm Salamah said:""Umm Habibah said: 'I heard the Messenger of Allah say: 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 mourns for him for) four months and ten (days)