Language:
كتاب الفرائض
85
Laws of Inheritance (Al-Faraa'id)
(21)
Chapter: The sin of the freed slave who denies his master who has freed him.
(21)
باب إِثْمِ مَنْ تَبَرَّأَ مِنْ مَوَالِيهِ
Sahih al-Bukhari 6756

Narrated Ibn `Umar:

The Prophet (ﷺ) forbade the selling of the Wala' (of slaves) or giving it as a present.

حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ نَهَى النَّبِيُّ صلى الله عليه وسلم عَنْ بَيْعِ الْوَلاَءِ وَعَنْ هِبَتِهِ‏.‏
Reference : Sahih al-Bukhari 6756
In-book reference : Book 85, Hadith 33
USC-MSA web (English) reference : Vol. 8, Book 80, Hadith 748
  (deprecated numbering scheme)