Hadith 4301
Sayyidah Aisha Siddiqa (may Allah be pleased with her) narrates: The Prophet Muhammad (peace and blessings be upon him) said: "It is not permissible for any woman who believes in Allah and the Last Day to mourn for anyone who has passed away for more than three days, except in the case of her husband; for him, she will mourn for four months and ten days."