Ibn Abbas (RA) reported: The Messenger of Allah (ﷺ) happened to pass by two graves and said: They (their occupants) are being tormented, but they are not tormented for a grievous sin. One of them carried tales and the other did not keep himself safe from being defiled by urine. He then called for a fresh twig and split it into two parts, and planted them on each grave and then said: Perhaps, their punishment way be mitigated as long as these twigs remain fresh.
This hadith is transmitted from A'mash by Abmad bin Yusuf al-Azdi, Mu'alla bin Asad, Abdul Wahid, Sulaiman with the same chain of transmitters but for the words: "The other did not keep himself safe from being defiled by urine."