Abu Ali al-Hamdani (may Allah have mercy on him) narrates: We were with Fadalah bin Ubayd (may Allah be pleased with him) at Rhodes in the land of the Romans when a companion of ours died. Fadalah (may Allah be pleased with him) gave orders about his grave and it was levelled. Then he said: I heard the Messenger of Allah (peace and blessings be upon him): he "used to order that they (graves) be levelled."
In a narration of Abu Salih (may Allah have mercy on him): Thumamah bin Shufayy (may Allah have mercy on him) says: We were with Fadalah bin Ubayd (may Allah be pleased with him) in the land of the Romans, and the rest of the hadith is the same as above.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6756