Sahih al-Bukhari 5342

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.