(58) باب الإِحْدَادِ
It was narrated from 'Aishah that the Prophet said:
"It is not permissible for a woman who believes in Allah and the Last Day to mourn for more than three days, except for her husband."
Reference: Sunan an-Nasa'i 3526
In-book reference: Book 27, Hadith 138
English translation: Vol. 4, Book 27, Hadith 3556