Sahih al-Bukhari 2726

Khallad ibn Yahya narrated to us; ʿAbd al-Wahid ibn Ayman al-Makki narrated to us, from his father, who said: I visited ʿAʾisha (may Allah be pleased with her). She said: Barira, who had a manumission contract, came to me and said, “Mother of the Believers, buy me, for my owners are selling me, then set me free.” I said, “Yes.” She said, “My owners will not sell me unless they stipulate that my walaʾ belongs to them.” I said, “I have no need of you.” The Prophet heard this, or it reached him, and he said, “What is the matter with Barira? Buy her and set her free, and let them stipulate whatever they wish.”

She said: I bought her and set her free, while her owners stipulated that her walaʾ belonged to them. The Prophet said, “Walaʾ belongs to the one who sets a person free, even if they stipulate a hundred conditions.”