(78) باب الْبَيْعِ يَكُونُ فِيهِ الشَّرْطُ الْفَاسِدُ فَيَصِحُّ الْبَيْعُ وَيَبْطُلُ الشَّرْطُ
It was narrated from'Abdullah bin 'Umar that 'Aishah wanted to but a slave woman to set her free, but her people said:
"We will sell her to you on condition that her loyalty (Walla) is to us," She mentioned that top the Messenger of Allah and he said: "That should not stop you. Loyalty belongs to the one who sets the slave free."
Reference: Sunan an-Nasa'i 4644
In-book reference: Book 44, Hadith 196
English translation: Vol. 5, Book 44, Hadith 4648