It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Sayyidah Aishah (may Allah be pleased with her) intended to buy a slave girl and set her free. Her owners said: We will sell her to you on condition that the wala' (the right of inheritance from the freed slave) is ours. Sayyidah Aishah (may Allah be pleased with her) told the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Do not let that hold you back, for the wala' belongs to the one who sets free."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12380