Sayyiduna Anas (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) passed by two graves (of two people) of Banu al-Najjar, who were being punished for spreading tales and because of urine. The Prophet (peace and blessings be upon him) took a palm branch, split it into two parts, placed one part on one grave and the other part on the other grave, and said: As long as these two (branches) remain fresh, the punishment of these two will remain lightened.
Imam Ahmad recorded it, and al-Tabarani in al-Mu'jam al-Awsat; its chain contains a narrator, Ubayd bin Abd al-Rahman, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1030