Jabir bin Abdullah reported,

The Prophet ﷺ decreed that each clan was responsible for paying the blood-money owed by its members, then he wrote, "It is not lawful for a Muslim to take as patron the freed slave of another Muslim without his permission." I was later informed that in his document he cursed anyone who did so.

Azami 8701

Sahih

عن جابر بن عبد الله يقول

كتب النبي ﷺ على كل بطن عقولهم ثم كتب: أن لا يحل لمسلم أن يتوالى مولى رجل مسلم بغير إذنه ثم أخبرت أنه لعن في صحيفته من فعل ذلك.

الأعظمي 8701صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Biography of the Prophet ﷺ
Chapter
Emigration of the Prophet ﷺ and his companions from Makkah to Madinah
Section
Brotherhood between the Muhajirun and the Ansar
Numbering
Jami al-Kamil 8701 (2nd edition)
Azami 8701