Thumamah bin Shufayy (may Allah have mercy on him) narrates: We were with Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) in the land of the Romans when a companion of ours died, so Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) ordered that his grave be levelled. He said: "I heard the Messenger of Allah (peace and blessings be upon him) say it, ordering that graves be levelled."
Hadith Referenceالمعجم الكبير للطبراني / باب الفاء / 15902