It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the daughter of Nu'aym bin Abdullah al-Adawi came to the Prophet (peace and blessings be upon him) and said: "My daughter's husband has died; she was married to al-Mughirah al-Makhzumi. She is now observing mourning, and she has a complaint in her eyes; may she apply kohl?" He (peace and blessings be upon him) said: "No." Then she remained silent for a while, then said: "She has more trouble in her eyes than we even thought; may she apply kohl?" He (peace and blessings be upon him) said: "No." Then he said: "It is not lawful for a Muslim woman to mourn for any deceased person for more than three days, except for a husband, for whom she mourns four months and ten days."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20120