Abu Dawud Book 34, Hadith Number 4515.
Narated By Ali ibn Abu Talib : Qays ibn Abbad and Ashtar went to Ali and said to him: Did the Apostle of Allah (PBUH) give you any instruction about anything for which he did not give any instruction to the people in general?
He said: No, except what is contained in this document of mine. Musaddad said: He then took out a document. Ahmad said: A document from the sheath of his sword.
It contained: The lives of all Muslims are equal; they are one hand against others; the lowliest of them can guarantee their protection. Beware, a Muslim must not be killed for an infidel, nor must one who has been given a covenant be killed while his covenant holds. If anyone introduces an innovation, he will be responsible for it. If anyone introduces an innovation or gives shelter to a man who introduces an innovation (in religion), he is cursed by Allah, by His angels, and by all the people.
Musaddad said: Ibn AbuUrubah’s version has: He took out a document.