The Prophet ﷺ wrote a document making each clan responsible for its own blood-money payments. He also wrote that it is not lawful for a Muslim to take the freed slave of another Muslim man as his client without that man's permission. I was then informed that in his document he cursed anyone who did so.
كتب النبي ﷺ على كل بطن عقوله، ثم كتب: أنه لا يحل لمسلم أن يتولى مولى رجل مسلم بغير إذنه. ثم أخبرت أنه لعن في صحيفته من فعل ذلك.