Sahih Muslim Book 9, Hadith Number 3550.

Chapter: It is obligatory to abstain from adornment during the ‘Idda period, but mourning beyond three days is prohibited.

Umm ‘Atiyya (Allah be pleased with her) reported that Allah’s Messenger (may peace be upon him) had said: A woman must not observe mourning for one who had died for more than three (days) except for four months and ten days in the case of her husband and she must not wear a dyed garment except one of the types made of dyed yarn, or apply collyrium, or touch perfume except a little perfume or incense, when she has been purified after her courses.