Sunan an-Nasa'i 3502

It was narrated from Zainab bint Umm Salamah, that Umm Salamah and Umm Habibah said:"A woman came to the Prophet and said: 'My daughter's husband has died, and I am worried about her eyes. Can I apply kohl to her?' The Messenger of Allah said: 'One of you used to stay (in mourning) for a year. Rather (the mourning period is) four months and ten (days). And when that year had passed she would go out and fling a piece of dung behind her