Narrated Ibn 'Abbas :

The Prophet (sal Allaahu alayhi wa sallam ) passed by two graves. He said : Both (the dead) are being punished, but they are not being punished for a major (sin). One did not safeguard himself from urine. The other carried tales. He then called for a fresh twig and split it into two parts and planted one part on each grave and said: Perhaps their punishment may be mitigated as long as the twigs remain fresh. Another version of Hannad has: "One of them did not cover himself while urinating." This version does not have the words: "He did not safeguard himself from urine."

حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَهَنَّادُ بْنُ السَّرِيِّ، قَالاَ حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا الأَعْمَشُ، قَالَ سَمِعْتُ مُجَاهِدًا، يُحَدِّثُ عَنْ طَاوُسٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ مَرَّ رَسُولُ اللَّهِ صلى الله عليه وسلم عَلَى قَبْرَيْنِ فَقَالَ ‏"‏ إِنَّهُمَا يُعَذَّبَانِ وَمَا يُعَذَّبَانِ فِي كَبِيرٍ أَمَّا هَذَا فَكَانَ لاَ يَسْتَنْزِهُ مِنَ الْبَوْلِ وَأَمَّا هَذَا فَكَانَ يَمْشِي بِالنَّمِيمَةِ ‏"‏ ‏.‏ ثُمَّ دَعَا بِعَسِيبٍ رَطْبٍ فَشَقَّهُ بِاثْنَيْنِ ثُمَّ غَرَسَ عَلَى هَذَا وَاحِدًا وَعَلَى هَذَا وَاحِدًا وَقَالَ ‏"‏ لَعَلَّهُ يُخَفَّفُ عَنْهُمَا مَا لَمْ يَيْبَسَا ‏"‏ ‏.‏ قَالَ هَنَّادٌ ‏"‏ يَسْتَتِرُ ‏"‏ ‏.‏ مَكَانَ ‏"‏ يَسْتَنْزِهُ ‏"‏ ‏.‏