Musannaf Ibn Abi Shayba 19:175

Abu Bakr narrated to us, he said: Abbad narrated to us, from Abd al-Malik, from Ata, regarding a man who accused a man whose mother was an *umm walad* (a slave woman who has borne a child to her master) of adultery. He said: There is no prescribed punishment (*hadd*) upon him until she is emancipated.