(67) باب الْبَيْعِ وَالشِّرَاءِ مَعَ النِّسَاءِ
Narrated `Abdullah bin `Umar:
Aisha wanted to buy Buraira and he (the Prophet (ﷺ) ) went out for the prayer. When he returned, she told him that they (her masters) refused to sell her except on the condition that her Wala' would go to them. The Prophet (ﷺ) replied, 'The Wala' would go to him who manumits.' " Hammam asked Nafi` whether her (Buraira's) husband was a free man or a slave. He replied that he did not know.
Reference: Sahih al-Bukhari 2156
In-book reference: Book 34, Hadith 107
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 34, Hadith 365