Sahih Bukhari Volume 8, Book 78, Hadith 6057

حَدَّثَنَا ابْنُ سَلاَمٍ، أَخْبَرَنَا عَبِيدَةُ بْنُ حُمَيْدٍ أَبُو عَبْدِ الرَّحْمَنِ، عَنْ مَنْصُورٍ، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ خَرَجَ النَّبِيُّ صلى الله عليه وسلم مِنْ بَعْضِ حِيطَانِ الْمَدِينَةِ، فَسَمِعَ صَوْتَ إِنْسَانَيْنِ يُعَذَّبَانِ فِي قُبُورِهِمَا فَقَالَ ‏"‏ يُعَذَّبَانِ، وَمَا يُعَذَّبَانِ فِي كَبِيرَةٍ، وَإِنَّهُ لَكَبِيرٌ، كَانَ أَحَدُهُمَا لاَ يَسْتَتِرُ مِنَ الْبَوْلِ، وَكَانَ الآخَرُ يَمْشِي بِالنَّمِيمَةِ ‏"‏‏.‏ ثُمَّ دَعَا بِجَرِيدَةٍ فَكَسَرَهَا بِكِسْرَتَيْنِ أَوْ ثِنْتَيْنِ، فَجَعَلَ كِسْرَةً فِي قَبْرِ هَذَا، وَكِسْرَةً فِي قَبْرِ هَذَا، فَقَالَ ‏"‏ لَعَلَّهُ يُخَفَّفُ عَنْهُمَا مَا لَمْ يَيْبَسَا ‏"‏‏.‏

Narrated By Ibn 'Abbas : Once the Prophet went through the grave-yards of Medina and heard the voices of two humans who were being tortured in their graves. The Prophet said, "They are being punished, but they are not being punished because of a major sin, yet their sins are great. One of them used not to save himself from (being soiled with) the urine, and the other used to go about with calumnies (Namima)." Then the Prophet asked for a green palm tree leaf and split it into two pieces and placed one piece on each grave, saying, "I hope that their punishment may be abated as long as these pieces of the leaf are not dried."