Sayyiduna (may Allah be pleased with him) narrates: The Prophet Muhammad (peace be upon him) wrote a letter to Bakr bin Wa'il. "From Muhammad, the Messenger of Allah, to Bakr bin Wa'il (this letter is): Accept Islam and you will be safe." The narrator states: So this letter was read by one of them who belonged to Banu Dubay'ah. That is why their name is Banu Katib (meaning they knew how to read and write).