Sahih al-Bukhari 4865

It is related that Umm 'Atiyya said, "It is not lawful for a woman who believes in Allah and the Last Day to mourn for a dead person more than three days unless it is her husband. She should not use kohl or dyed clothes except for an 'asb garment." It is related from Hafsa from Umm 'Atiyya, "The Prophet, may Allah bless him and grant him peace, forbade her to use perfume except when she first becomes pure when she can use a piece of qust and azfar." Abu 'Abdullah [al-Bukhari] said, "Qust and kust are like kafur and qafur." Nubdha means a piece. XLVIII. "Those of you who die leaving wives behind: they should wait by themselves for four months and ten nights. When their waiting-period comes to an end, you are not to blame for anything they do with themselves with correctness and courtesy. Allah is aware of everything you do." (2:234)