Kharijah bin Zayd bin Thabit narrates from his father (Sayyiduna Zayd bin Thabit, may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) ordered me, so I learned the writing of the Jews for him. He had said: "By Allah! I do not trust the Jews with my correspondence." So I learned it, and not even half a month had passed before I became proficient in it. He said: Then whenever he (peace and blessings be upon him) had letters written to the Jews I would write them, and whenever a letter came from them I would read it out to him (peace and blessings be upon him). This hadith is sahih (authentic), and I do not know of any other hadith besides this one regarding the permission to learn the writing of the People of the Book.