(9) باب وُجُوبِ الإِحْدَادِ فِي عِدَّةِ الْوَفَاةِ وَتَحْرِيمِهِ فِي غَيْرِ ذَلِكَ إِلاَّ ثَلاَثَةَ أَيَّامٍ
Safiyya bint Abu 'Ubaid reported that she heard Hafsa daughter of Umar (Allah be pleased with them), (and) wife of Allah's Prophet (ﷺ), narrating a hadith like this from Allah's Apostle (ﷺ), and she made this addition:
" She should abstain from adorning herself (in case of the death of her husband) for four months and ten days."
Reference: Sahih Muslim 1490 c
In-book reference: Book 18, Hadith 82
USC-MSA web (English) reference(deprecated numbering scheme): Book 9, Hadith 3547