Musnad Ahmad 993

It was narrated that Qais bin ‘Ubad said: I set out with al-Ashtar to go to ‘Ali (رضي الله عنه). We said: Did the Prophet (ﷺ) of Allah (ﷺ) tell you something that he did not tell to all the people? He said: No, except what is in this document. He [the narrator] said: A document in the sheath of this sword. In it was said: “The believers are equal in respect of blood and they are one against their enemies; protection given even by the least among them is to be honoured, but no believer is to be killed (in retaliation) for a disbeliever and no one who has a covenant is to be killed during the covenant. Whoever commits an offence or gives refuge to an offender, upon him be the curse of Allah, the angels and all the people.`