It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) forbade plastering graves, writing on them, building over them and sitting on them. These chains are sahih (authentic), but (in practice) they are not acted upon, for the graves of the Imams of the Muslims from the East to the West have writing on them, and this is a practice that the later generations (khalaf) took from the earlier ones (salaf).