(1)
Abu Hurairah (RAA) narrated regarding the story of the black woman who used to clean the mosque. The Messenger of Allah asked about her, and he was told that she had died. He said to them, "Why didn't you inform me of her death?" It seems that they regarded her as an insignificant person. The Messenger of Allah (ﷺ) said:
"Show me her grave." They showed him her grave and he offered the funeral prayer for her.' Agreed upon. Muslim added in his narration, 'Verily, those graves are full of darkness for those buried in them. Allah, the Almighty, will illuminate them for their dwellers by my prayer over them"
Reference: Bulugh al-Maram 555
In-book reference: Book 3, Hadith 23
English translation: Book 3, Hadith 579