The Book of Faith (Kitab Al-Iman)
Muslim :: Book 1 : Hadith 5
This hadith is narrated to us on the authority of Muhammad b. 'Abdullah b. Numair, on the authority of Muhammad b. Bishr, on the authority of Abd Hayyan al-Taymi with the exception that in this narration (instead of the words (Iza Waladat al'amah rabbaha), the words are (Iza Waladat al'amah Ba'laha), i, e, when slave-girl gives birth to her master.