Hadith 514840
Chapter 38: Setting Free and Wala' - كتاب العتق والولاء
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, may Allah bless him and grant him peace, forbade selling or giving away the wala'.
Reference Muwatta Malik 514840
USC-MSA web (English) reference : Book 38, Hadith 20