Abu Dawud Book 12, Hadith Number 2909.
Chapter : Right of inheritance of the property of a freed slave.
Narated By Ibn ‘Umar : ‘Aisha, mother of the believers (Allah be pleased with her), intended to buy a slave girl to set her free. Her people said: We shall sell her to you on the condition that we shall inherit from her. ‘Aisha mentioned it to the Apostle of Allah (PBUH). He said: That should not prevent you, for the right of inheritance belongs to the one who has set a person free.