5. Ali has narrated from his father from Ibn Abi ‘Umayr from Muhammad ibn Ishaq ibn ‘Ammar from abu al-Hassan Musa عليه السلام who has said the following: “The Imam عليه السلام was asked about the surfaces on which a mention of Allah, the Most Majestic, the Most Holy, is written. The Imam said, ‘Wash it clean.’”