Sahih Muslim Book 9, Hadith Number 3544.

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

Zainab bint Abu Salama reported that when the news of the death of Abu Sufyan came to Umm Habiba she sent for yellow (perfume) on the third day and rubbed it on her forearms and on her cheeks and said: I had in fact no need of it, but I heard Allah’s Messenger (may peace be upon him) as saying: It is not permissible for the women believing in Allah and the Hereafter to abstain from adornment beyond three days except (at the death of) husband (in which case she must abstain from adornment) for four months and ten days.