Sahih Muslim Book 9, Hadith Number 3597.

Chapter: It is forbidden to sell Al-Wala’ (the right of inheritance of a slave) and its conferring on others.

This hadith has been narrated on the authority of Ibn ‘Umar (Allah be pleased with them) through another chain of transmitters but with this change that in the hadith narrated by al-Thaqafi from Ubaidullah there is only a mention of selling (or right of inheritance, al-Wala’) but not that of making a gift.