"It is not permissible for a woman who believes in Allah and the Last Day to mourn for anyone who dies for more than three days except for a husband; she should mourn for him for four months and ten (days)." (Using translation from Nasāʾī 3503)
أَنَّهَا سَمِعَتْ حَفْصَةَ بِنْتَ عُمَرَ زَوْجَ النَّبِيِّ ﷺ عَنِ النَّبِيِّ ﷺ قَالَ «لَا يَحِلُّ لِامْرَأَةٍ تُؤْمِنُ بِاللهِ وَالْيَوْمِ الْآخِرِ أَنْ تُحِدَّ فَوْقَ ثَلَاثٍ إِلَّا عَلَى زَوْجٍ فَإِنَّهَا تُحِدُّ عَلَيْهِ أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا»