Musnad Ahmad 356, 357

Muhammad ibn Ja‘far narrated to us; Shu‘bah narrated to us; Hajjaj narrated to us. He said: Shu‘bah narrated to me, from Qatadah, who said: I heard Abu ‘Uthman al-Nahdi say: ‘Umar’s letter came to us when we were in Adharbayjan with ‘Utbah ibn Farqad—or in Syria. It said: To proceed: The Messenger of Allah, peace and blessings be upon him, forbade silk except for this much—two fingers.’ Abu ‘Uthman said: We had no doubt that he meant the embroidered borders. Muhammad ibn Ja‘far narrated to us; Shu‘bah, Hajjaj, and Abu Dawud narrated to us; he said: Shu‘bah narrated to us, from Qatadah, who said: I heard Abu ‘Uthman al-Nahdi say: ‘Umar’s letter came to us…’