(30) باب إِحْدَادِ الْمَرْأَةِ عَلَى غَيْرِ زَوْجِهَا
Narrated Zainab bint Abi Salama:
I went to Um Habiba, the wife of Prophet, who said, "I heard the Prophets saying, 'It is not legal for a woman who believes in Allah and the Last Day to mourn for any dead person for more than three days except for her husband, (for whom she should mourn) for four months and ten days'." Later I went to Zainab bint Jahsh when her brother died; she asked for some scent, and after using it she said, "I am not in need of scent but I heard Allah's Messenger (ﷺ) saying, 'It is not legal for a woman who believes in Allah and the Last Day to mourn for more than three days for any dead person except her husband, (for whom she should mourn) for four months and ten days.' "
Reference: Sahih al-Bukhari 1281, 1282
In-book reference: Book 23, Hadith 43
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 23, Hadith 371