Sayyiduna Marthad bin Zabyan (may Allah be pleased with him) narrates: A letter from the Messenger of Allah came to us, and we found no one who could read it out to us, until a man from Banu Dubay'ah read it out: "This is from the Messenger of Allah to Bakr bin Wa'il: Accept Islam and you will be safe."
Ahmad recorded it, and its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجهاد / 9580
Hadith Gradingمحدثین:إسنادہ صحیح۔
Hadith Takhrij«اخرجه احمد فى المسند (68/5) ، أخرجه مسند أحمد برقم: 20144»