Musnad Ahmad 32:1883

'Affan narrated to us, Hammad narrated to us, from Thabit, from Anas, that Quraysh made a peace treaty with the Prophet, may God bless him and grant him peace, and among them was Suhayl ibn 'Amr. The Prophet, may God bless him and grant him peace, said to 'Ali: "Write: In the name of God, the Most Gracious, the Most Merciful." Suhayl said: "As for 'In the name of God, the Most Gracious, the Most Merciful,' we do not know what 'In the name of God, the Most Gracious, the Most Merciful' is. But write what we know: 'In Your name, O God.'" He said: "Write: From Muhammad, the Messenger of God." He said: "If we knew that you were the Messenger of God, we would have followed you. But write your name and the name of your father." The Prophet, may God bless him and grant him peace, said: "Write: From Muhammad ibn 'Abdullah." They stipulated to the Prophet, may God bless him and grant him peace, that whoever comes to you from us, we will not return him to you, and whoever comes to us from you, you will return him to us. He [the narrator] said: "O Messenger of God, will you write this?" He said: "Yes, for whoever goes from us to them, may God distance him."