Sahih al-Bukhari 5335
Zainab further said:
I want to Zainab bint Jahsh when her brother died. She 
asked for perfume and used some of it and said, "By Allah, I am not in need of perfume, but I have 
heard Allah's Messenger (ﷺ) saying on the pulpit, 'It is not lawful for a lady 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.'"
قَالَتْ زَيْنَبُ فَدَخَلْتُ عَلَى زَيْنَبَ ابْنَةِ جَحْشٍ حِينَ تُوُفِّيَ أَخُوهَا، فَدَعَتْ بِطِيبٍ فَمَسَّتْ مِنْهُ، ثُمَّ قَالَتْ أَمَا وَاللَّهِ مَا لِي بِالطِّيبِ مِنْ حَاجَةٍ غَيْرَ أَنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ عَلَى الْمِنْبَرِ ‏
"‏ لاَ يَحِلُّ لاِمْرَأَةٍ تُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ أَنْ تُحِدَّ عَلَى مَيِّتٍ فَوْقَ ثَلاَثِ لَيَالٍ إِلاَّ عَلَى زَوْجٍ أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا ‏"‏‏.‏