The sin of the freed slave who denies his master who has freed him.
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.
Narrated Ibn `Umar: The Prophet (ﷺ) forbade the selling of the Wala' (of slaves) or giving it as a present.