"Umm Habibah said: 'I heard the Messenger of Allah say: 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 mourns for him for) four months and ten (days)." (Using translation from Nasāʾī 3500)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ لَا يَحِلُّ لِامْرَأَةٍ تُؤْمِنُ بِاللهِ وَالْيَوْمِ الْآخِرِ أَنْ تُحِدَّ فَوْقَ ثَلَاثَةِ أَيَّامٍ إِلَّا عَلَى زَوْجِهَا