Sayyidah Zaynab bint Umm Salamah (may Allah be pleased with her) said: I went to Sayyidah Zaynab bint Jahsh (may Allah be pleased with her) when her brother died. She called for perfume and applied some of it, then said: I have no need of perfume, but I heard the Messenger of Allah (peace and blessings be upon him) say: "It is not lawful for a woman who believes in Allah and the Last Day to mourn for a deceased person for more than three days, except for a husband, for whom she mourns four months and ten days."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20511