Sunan at-Tirmithiy كتاب الرضاع باب ما جاء فى لبن الفحل
Ibn-'Abbās was asked about a man who had two bondswomen, one having breastfed a little girl and the other one a little boy, if it was permissible (as defined by God) for the boy to marry the girl. "No," he replied, "the seminal fluid (1) is the same." (2) Footnotes: (1) which caused the women's pregnancies and their consequent ability to lactate. (2) This is the view held by Aḥmad and Isḥāq. Click on ḥadīth to read more