The Prophet ﷺ said, "It is not lawful for a Muslim woman who believes in Allah and the Last Day to mourn for more than three days, except for her husband, for whom she should mourn for four months and ten days."
أَنَّ النَّبِيَّ ﷺ قَالَ لاَ يَحِلُّ لاِمْرَأَةٍ مُسْلِمَةٍ تُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ أَنْ تُحِدَّ فَوْقَ ثَلاَثَةِ أَيَّامٍ إِلاَّ عَلَى زَوْجِهَا أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا