Muwatta Imam Malik Book of Divorce, Hadith 102

Zaynab said, "I went to the house of Zaynab bint Jahsh, the wife of the Prophet ﷺ when her brother had died. She called for perfume and put some on and said, 'By Allah! I have no need of perfume, but I heard the Messenger of Allah ﷺ say, 'It is not halal for a woman who trusts in Allah and the Last Day to abstain from adornment in mourning for someone who has died for more than three nights, except for four months and ten days for a husband.' "

قَالَتْ زَيْنَبُ ثُمَّ دَخَلْتُ عَلَى زَيْنَبَ بِنْتِ جَحْشٍ زَوْجِ النَّبِيِّ ﷺ حِينَ تُوُفِّيَ أَخُوهَا فَدَعَتْ بِطِيبٍ فَمَسَّتْ مِنْهُ ثُمَّ قَالَتْ وَاللَّهِ مَا لِي بِالطِّيبِ حَاجَةٌ غَيْرَ أَنِّي سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ " لاَ يَحِلُّ لاِمْرَأَةٍ تُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ تُحِدُّ عَلَى مَيْتٍ فَوْقَ ثَلاَثِ لَيَالٍ إِلاَّ عَلَى زَوْجٍ أَرْبَعَةَ أَشْهُرٍ وَعَشْرًا " .