Sahih Muslim Book 9, Hadith Number 3539.
Chapter: It is obligatory to abstain from adornment during the ‘Idda period, but mourning beyond three days is prohibited.
Zainab (bint Abu Salama) (Allah be pleased with her) reported: I went to Umm Habiba, the wife of Allah’s Apostle (may peace be upon him), when her father Abu Sufyan had died. Umm Habiba sent for a perfume having yellowness in it or something else like it, and she applied it to a girl and then rubbed it on her cheeks and then said: By Allah, I need no perfume but for the fact that I heard Allah’s Messenger (may peace be upon him) say on the pulpit: “It is not permissible for a woman believing in Allah and the Hereafter to mourn for the dead beyond three days, but (in case of the death) of the husband it is permissible for four months and ten days.” Zainab said: I then visited Zainab hint Jahsh (Allah be pleased with her) when her brother died and she sent for perfume and applied it and then said: By Allah, I don’t feel any need for the perfume but that I heard Allah’s Messenger (may peace be upon him) say on the pulpit: “It is not permissible for a woman believing in Allah and the Hereafter to mourn the dead beyond three days except in case of her husband (for whom she can mourn) for four months and ten days.” Zainab (Allah be pleased with her) said: I heard my mother Umm Salama (Allah be pleased with her) as saying: A woman came to Allah’s Messenger (may peace be upon him) and said: Allah’s Messenger. I have a daughter whose husband has died and there has developed some trouble in her eye; should we apply collyrium to it? Thereupon Allah’s Messenger (may peace be upon him) said: No (repeating it twice or thrice, saying only ,NO” all the time). Then he said: It is only four mouths and ten days, whereas in the pre Islamic period none of you threw away the dung until one year had passed. Humaid said: I said to Zainab: What is this throwing of dung until a year is passed? Zainab said: When the husband of a woman died, she went into a hut and put on her worst clothes, and did not apply perfume or something like it until a year was over. Then an animal like a donkey, or a goat, or a bird was brought to her and she rubbed her hand over it, and it so happened that one on which she rubbed her hand died. She then came out of her house and she was given dung and she threw it and then she made use of anything like perfume or something else as she liked.