Abu Dawud Book 24, Hadith Number 3937.
Chapter : The view that a slave will not be required to work for purchasing his freedom.
Narated By N/A : Ibn al-Thalabb reported on the authority of his father: A man emancipated his share in a slave. The Prophet (may peace be upon him) did not put the responsibility on him to emancipate the rest.
Ahmad said: The name Ibn al-Thalabb is to be pronounced with ta’ (and not with tha). As Shu’bah could not pronounce ta, he said tha.