Sahih Muslim Book 19, Hadith Number 4402.

Chapter : The treaty of Hudaibiya.

It has been narrated on the authority of Abu Ishaq, who heard Bars’ b. Azib say: When the Messenger of Allah (may peace be upon him) made peace with the people of Hudaibiya, ‘Ali drew up the agreement between them, and so he wrote: Muhammad, the Messenger of Allah. (This is followed by the same wording as we have in the previous tradition except the omission of the words: This is what he has settled.)