The Prophet ﷺ once passed by two graves and said, "These two persons are being tortured not for a major sin (to avoid). One of them never saved himself from being soiled with his urine, while the other used to go about with calumnies (to make enmity between friends)." The Prophet ﷺ then took a green leaf of a date-palm tree, split it into (pieces) and fixed one on each grave. They said, "O Allah's Apostle! Why have you done so?" He replied, "I hope that their punishment might be lessened till these (the pieces of the leaf) become dry." (See the footnote of Hadith 215). (Using translation from Bukhārī 218)   

مَرَّ رَسُولُ اللهِ ﷺ بِقَبْرَيْنِ فَقَالَ إِنَّهُمَا لَيُعَذَّبَانِ وَمَا يُعَذَّبَانِ فِي كَبِيرٍ أَمَّا أَحَدُهُمَا فَكَانَ يَمْشِي بِالنَّمِيمَةِ وَأَمَّا الْآخَرُ فَكَانَ لَا يَسْتَتِرُ مِنَ الْبَوْلِ ثُمَّ أَخَذَ جَرِيدَةً رَطْبَةً فَشَقَّهَا نِصْفَيْنِ ثُمَّ جَعَلَ فِي كُلِّ قَبْرٍ وَاحِدَةً قَالَ قَالُوا يَا رَسُولَ اللهِ لِمَ فَعَلْتَ هَذَا؟ قَالَ لَعَلَّهُ أَنْ يُخَفَّفَ عَنْهُمَا مَا لَمْ يَيْبَسَا