Narrated Ibn `Umar
Allah's Messenger (ﷺ) forbade the selling or donating the Wala' of a freed slave.
Narrated `Aisha
I bought Buraira but her masters put the condition that her Wala' would be for them. I told the Prophet (ﷺ) about it. He said (to me), "Manumit her as her Wala' will be for the one who pays the price." So, I manumitted her. The Prophet (ﷺ) called Buraira and gave her the option of either staying with her husband or leaving him. She said, "Even if he gave me so much money, I would not stay with him," and so she preferred her freedom to her husband.