«اِلْوِسْخَهْ تِفْرَحْ لِيُومِ الْحُزْنْ»

On a day of mourning nobody washes up, dresses well, or puts on ornaments. A woman who is always unkempt therefore has a rare chance to look no worse than anyone else. For her, the sorrow everyone shares becomes a quiet relief, because the usual contrast that shames her disappears.

More broadly, the saying mocks people who lack merit or effort and are pleased when circumstances drag everyone down to their level. They do not rise to meet a standard. Instead they welcome any occasion that removes the standard, so that their deficiency blends in and nobody can outshine them.

Use it with care to mock someone who welcomes mourning or austere occasions because they hide that person's shortcomings. The subject is feminine and 'dirty' can be a harsh insult, so aimed at a real person it may sound demeaning and gendered; it suits informal, critical remarks, not polite conversation.