Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated: The Messenger of Allah (peace and blessings be upon him) passed by a grave, stopped there, and asked for two date palm branches. He placed one at the head and the other at the feet of the grave, then said: "It is possible that as long as there is moisture (wetness) in them, Allah may lighten their punishment in the grave."
Hadith Referenceمسند اسحاق بن راهويه / كتاب أحوال الاخرة / 948