Maliks Muwatta Book 29, Hadith Number 102.
Section : Limit of Abstaining from Adornment in Mourning.
Zaynab said, “I went to the house of Zaynab bint Jahsh, the wife of the Prophet, may Allah bless him and grant him peace, 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, may Allah bless him and grant him peace, 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.'”