سنن النسائي

Zainab bint Abi Salamah narrated that her mother Umm Salamah said: "A woman from the Quraish came and said: 'O Messenger of Allah, my daughter's eyes are inflamed; shall I apply kohl to her?' (The daughter's) husband had died so (the Prophet) said: 'Not until four months and ten days (have passed).' Then she said: 'I fear for her sight.' He said: 'No, not until four months and ten days (have passed). During the Jahiliyyah one of you would mourn for her husband for a year, then when one year had passed she would throw a piece of dung.'"