Sunan an-Nasa'i 4746

It was narrataed from Al-Ashtar that he said to 'Ali:"What the people have been hearing from you has become widespread. If the Messenger of Allah told you anything, then tell us," He said: "The Messenger of Allah did not tell me anything that he did not tell the people, except that in the sheath of my sword there is a sheet, in which it says: 'The lives of the believers are equal in value, and they hasten to support the asylum granted by the least of them. But no believer may be killed in return for a disbeliever, nor one with a covenant while his covenant is in effect."' It is an abridgement of it