Sunan Abi Dawud — The Book of Manumission of Slaves — Hadith No: 3942
Translation
The tradition mentioned above has also been narrated by Ibn 'Umar from the Prophet (ﷺ). The narrator Ayyub said:I do not know whether the following words are part of the tradition of the Prophet (ﷺ) or Nafi' told them himself: "Otherwise he will be emancipated to the extent of the first man's share