Abu Dawud Book 24, Hadith Number 3931.
Chapter : The view that a slave will not be required to work for purchasing his freedom.
Narated By N/A : The tradition mentioned above has also been narrated by Ibn Umar from the Prophet (may peace be upon him). The narrator Ayyub said: I do not know whether the following words are a part of the tradition of the Prophet (may peace be upon him) or Nafi’ told them himself: “otherwise he will be emancipated to the extent of the first man’s share.”