The Messenger of Allah ﷺ commanded me to learn the writing of the Jews for him. He said, "By Allah, I do not trust the Jews with my correspondence."So I learned it, and not even half a month passed before I had mastered it. I would write for him whenever he sent letters, and read to him whenever letters were sent to him.
أمرني رسول الله ﷺ فتعلمت له كتاب يهود وقال: إني والله ما آمن يهود على كتابي. فتعلمته، فلم يمر إلا نصف شهر حتى حذقته، فكنت أكتب له إذا كتب، وأقرأ له إذا كتب إليه.
Abu Dawud (3645) and Tirmidhi (2715) both narrated it through Abdul-Rahman bin Abu Zinad, from his father, from Kharija bin Zayd bin Thabit, from his father Zayd bin Thabit, who related the hadith. Its chain of transmission is sahih, and Hakim (1/75) graded it sahih, narrating it through this same route.Imam Ahmad (21587) narrated it through another route from Zayd, who said, "The Messenger of Allah ﷺ said to me, 'Do you know Syriac? Letters come to me.' I said, 'No.' He said, 'Then learn it.' So I learned it in seventeen days."Bukhari mentioned it without a full chain in his Sahih, saying, "Kharija bin Zayd bin Thabit said, on the authority of Zayd bin Thabit, that the Prophet ﷺ instructed him to learn the writing of the Jews."Ibn Hajar said in Fath al-Bari (13/161), "He narrated it with a complete chain and at length in his book Al-Tarikh."