Explanation
Islam came and relieved people of the hardship of the pre-Islamic era, especially the woman, who was mistreated and wronged but Islam preserved her rights.
In this Hadīth, a woman came seeking a legal ruling from the Prophet (may Allah's peace and blessings be upon him) as she told him that her daughter’s husband had died and that her daughter was in her mourning period, during which she had to abstain from adornment. However, she complained about some pain in her eyes. The woman asked whether there was a concession allowing her daughter to use Kohl.
The Prophet (may Allah's peace and blessings be upon him) said: "No", repeating it in confirmation of his disapproval.
Then he made a remark about the considerable shortness of the duration of a widow’s period of mourning as a veneration of the husband, which is four months and ten days. Then he wondered why women would not endure this short period that involved ease and comfort?
In the pre-Islamic era, a widow would observe the mourning period in a small house, like a den in the wilderness, and for a full year she would abstain from adornment, perfume, water, and mixing with people, such that the filth and dirt would accumulate on her body, while being secluded from people.
When her mourning period ended, she would be given a piece of dung, which she would then throw away, as an indication that what she went through of confinement, hardship and difficulty is as insignificant as that piece of dung when compared to her husband's huge right upon her.
When Islam came, it replaced such a distress with favor, and such a difficulty with ease. However, women were too impatient to refrain from applying Kohl to their eyes. That is why no concession was granted to such a woman in this case, in order not to be a means leading to allowing adornment for a woman in her mourning period.