The Messenger of Allah ﷺ forbade the sale of the right of patronage and its gifting.
حدثنا حفص بن عمر حدثنا شعبة عن عبد الله بن دينار
نهى رسول الله ﷺ عن بيع الولاء وعن هبته
Bukhari narrated it in the Book of Manumission, chapter "The Sale and Gifting of Right of Inheritance from a Freed Slave," Hadith 2535, and Muslim narrated it in the Book of Manumission, chapter "The Prohibition of Selling and Gifting Right of Inheritance from a Freed Slave," Hadith 1506, from the hadith of Shubah, through this same chain.