Sahih al-Bukhari 4862

It is related from Zaynab, the daughter of Umm Salama from her mother that a woman was widowed and they feared for her eyes and went to the Messenger of Allah, may Allah bless him and grant him peace, and asked him for permission for to use kohl. He said, "She should not use kohl. One of you would remain in the worst of her clothes or the worst room and after a year, if a dog passed by her, she would throw a piece of dung. Now (mourning) is only for four months and ten days." Humayd said, "I heard Zaynab, the daughter of Umm Salama, reporting from Umm Habiba that the Prophet, may Allah bless him and grant him peace, said, "It is not lawful for a Muslim woman who believes in Allah and the Last Day to mourn for a dead person more than three unless it is her husband. She should mourn him for four months and ten days."