It is narrated from Humaid bin Nafi that Zainab bint Abi Salamah related three hadiths to him. The first is that I went to Lady Umm Habibah (may Allah be pleased with her), who was the wife of the Prophet (peace be upon him), when her father Abu Sufyan bin Harb had died. Lady Umm Habibah (may Allah be pleased with her) asked for perfume in which there was some yellow coloring, and after applying it to a slave girl, she applied it to her own cheeks and said, "By Allah! I have no need for perfume, but I heard the Messenger of Allah (peace be upon him) say: 'It is not permissible for a woman who believes in Allah and the Last Day to mourn for any deceased person for more than three days, except for her husband, for whom she should mourn for four months and ten days.'"
The second hadith is that Lady Zainab (may Allah be pleased with her) said: I went to Lady Zainab bint Jahsh (may Allah be pleased with her), who was the wife of the Prophet (peace be upon him). When her brother died, she asked for perfume and applied it, and said: "By Allah! I have no need for perfume, but I heard the Messenger of Allah (peace be upon him) say: 'It is not permissible for a woman who believes in Allah and the Last Day to mourn for any deceased person for more than three days, except for her husband, for whom she should mourn for four months and ten days.'"
The third hadith is that Lady Zainab (may Allah be pleased with her) said: I went to my mother, Lady Umm Habibah (may Allah be pleased with her), who was the wife of the Prophet (peace be upon him). She said: A woman came to the Prophet (peace be upon him) and said: "O Messenger of Allah (peace be upon him)! My daughter's husband has died and her eyes are hurting; if you permit, may I apply kohl to her eyes?" The Prophet (peace be upon him) said: "No, no," two or three times, then said: "Rather, it is necessary to abstain for four months and ten days, and in the time of ignorance, they used to abstain for a whole year. When the year ended, they would throw a camel's dung." Humaid said: I asked Lady Zainab (may Allah be pleased with her): "What is meant by throwing a camel's dung?" She said: "In the time of ignorance, when a woman's husband died, she would go to a ruin and wear the worst of clothes, and would not apply any perfume or anything else for a year. After the year, they would bring an animal, a donkey or a goat or some bird, and she would rub it on her body, and often it would die. After that, when she came out, they would give her a camel's dung, and by throwing it away, she would then have the choice—if she wished, she could apply perfume or do any other thing."