Abu Dawud Book 24, Hadith Number 3944.
Chapter : Freedom of a slave after the death of his master mudabbar.
Narated By N/A : Jabir b. ‘Abd Allah said: A man declared that his slave would be free after his death, but he had no other property. So the Prophet (may peace be upon him) ordered (to sell him). He was then sold for seven hundred or nine hundred (dirhams).