مُوَطَّأُ مَالِكٍ
Muwatta Malik 1485
Setting Free and Wala'
وَحَدَّثَنِي مَالِكٌ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنْ بَيْعِ الْوَلاَءِ وَعَنْ هِبَتِهِ .
Malik related to me from Abdullah ibn Dinar from Abdullah ibn Umar that the Messenger of Allah, (ﷺ), forbade selling or giving away the wala'.
Arabic/English book reference: Book 38, Hadith 20