Sahih Muslim , Book 4, Hadith 2088 (USC-MSA) ⓘ

It is narrated on the authority of Abu Huraira that a dark-complexioned woman (or a youth) used to sweep the mosque. The Messenger of Allah missed her (or him) and inquired about her (or him). The people told him that she (or he) had died. He asked why they did not inform him, and it appears as if they had treated her (or him) or her (or his) affairs as of little account. He (the Holy Prophet) said: Lead me to her (or his) grave. They led him to that place and he said prayer over her (or him) and then remarked: Verily, these graves are full of darkness for their dwellers. Verily, the Mighty and Glorious Allah illuminates them for their occupants by reason of my prayer over them.

وَحَدَّثَنِي أَبُو الرَّبِيعِ الزَّهْرَانِيُّ، وَأَبُو كَامِلٍ فُضَيْلُ بْنُ حُسَيْنٍ الْجَحْدَرِيُّ - وَاللَّفْظُ لأَبِي كَامِلٍ - قَالاَ حَدَّثَنَا حَمَّادٌ، - وَهُوَ ابْنُ زَيْدٍ عَنْ ثَابِتٍ الْبُنَانِيِّ، عَنْ أَبِي رَافِعٍ، عَنْ أَبِي، هُرَيْرَةَ أَنَّ امْرَأَةً، سَوْدَاءَ كَانَتْ تَقُمُّ الْمَسْجِدَ - أَوْ شَابًّا - فَفَقَدَهَا رَسُولُ اللَّهِ صلى الله عليه وسلم فَسَأَلَ عَنْهَا - أَوْ عَنْهُ - فَقَالُوا مَاتَ ‏.‏ قَالَ ‏"‏ أَفَلاَ كُنْتُمْ آذَنْتُمُونِي ‏"‏ ‏.‏ قَالَ فَكَأَنَّهُمْ صَغَّرُوا أَمْرَهَا - أَوْ أَمْرَهُ - فَقَالَ ‏"‏ دُلُّونِي عَلَى قَبْرِهِ ‏"‏ ‏.‏ فَدَلُّوهُ فَصَلَّى عَلَيْهَا ثُمَّ قَالَ ‏"‏ إِنَّ هَذِهِ الْقُبُورَ مَمْلُوءَةٌ ظُلْمَةً عَلَى أَهْلِهَا وَإِنَّ اللَّهَ عَزَّ وَجَلَّ يُنَوِّرُهَا لَهُمْ بِصَلاَتِي عَلَيْهِمْ ‏"‏ ‏.‏