Sahih Bukhari
Expiation for Unfulfilled Oaths
Volume: 008 / Book Number: 079 / Hadith Number: 708
Narrated 'Aisha:
that she intended to buy Barira (a slave girl) and her masters stipulated that they would have her Wala'. When 'Aisha mentioned that to the Prophet ; he said, "Buy her, for the Wala' is for the one who manumits."