Sahih al-Bukhari Book 68, Hadith 81
"I heard my mother, Um Salama saying that a woman came to Allah's Messenger (ﷺ)
and said, "O Allah's Messenger (ﷺ)! The husband of my daughter has died and she is suffering from an eye
disease, can she apply kohl to her eye?" Allah's Messenger (ﷺ) replied, "No," twice or thrice. (Every time she
repeated her question) he said, "No." Then Allah's Messenger (ﷺ) added, "It is just a matter of four months
and ten days. In the Pre-Islamic Period of ignorance a widow among you should throw a globe of
dung when one year has elapsed."
I want to Zainab bint Jahsh when her brother died. She asked for perfume and used some of it and said, "By Allah, I am not in need of perfume, but I have heard Allah's Messenger (ﷺ) saying on the pulpit, 'It is not lawful for a lady who believes in Allah and the last day to mourn for more than three days except for her husband for whom she should mourn for four months and ten days.'"
I (Humaid) said to Zainab, "What does 'throwing a globe of dung when one year had elapsed' mean?" Zainab said, "When a lady was bereaved of her husband, she would live in a wretched small room and put on the worst clothes she had and would not touch any scent till one year had elapsed. Then she would bring an animal, e.g. a donkey, a sheep or a bird and rub her body against it. The animal against which she would rub her body would scarcely survive. Only then she would come out of her room, whereupon she would be given a globe of dung which she would throw away and then she would use the scent she liked or the like."