Ayesha wanted to buy a slave girl in order to set her free, but her owners refused unless the right of guardianship would remain with them. She mentioned this to the Messenger of Allah ﷺ, who said, "Do not let that stop you, for the right of guardianship belongs only to the one who sets the slave free."
أرادت عائشة أن تشترى جارية تعتقها، فأبى أهلها إلا أن يكون لهم الولاء، فذكرت ذلك لرسول الله ﷺ فقال: لا يمنعك ذلك؛ فإنما الولاء لمن أعتق.
Muslim narrated it in the chapter on manumission (1505), from Abu Bakr bin Abu Shayba, who said, Khalid bin Mukhlad narrated to us, from Sulayman bin Bilal, who said, Suhayl bin Abu Salih narrated to me, from his father, from Abu Hurairah, and he related it.