Umm Salama bint Abu Umaya reported,

A woman's husband died, and her family feared for her eyes, so they came to the Messenger of Allah ﷺ and asked his permission for her to use kohl.He said, "Do not apply kohl. One of you used to remain in the worst of her garments, or in the worst part of her house, and when a year had passed and a dog passed by, she would throw a piece of dung. No, not until four months and ten days have passed."

Azami 6663

Sahih

عن أم سلمة

أن امرأة توفي عنها زوجها، فخشوا عينيها فأتوا رسول الله ﷺ فاستأذنوه في الكحل فقال: لا تكحل، قد كانت إحداكن تمكنت في شر أحلاسها، أو شر بيتها، فإذا كان حول فمر كلب رمت ببعرة، فلا حتى تمضي أربعة أشهر وعشرا.

الأعظمي 6663صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Waiting period, mourning, and maintenance
Section
Prohibition of using kohl during mourning
Numbering
Jami al-Kamil 6663 (2nd edition)