Musannaf Ibn Abi Shayba 9:343

'Abd al-A'la ibn 'Abd al-A'la narrated to us, from Muhammad ibn Ishaq, from Abu al-Zinad, from 'Abd Allah ibn Yasar al-Aslami, who said: I had a slave girl whom I used to have intercourse with, and she had a daughter with her. Her daughter reached puberty, and I wanted to ask about her and look at her daughter. She said: "I will not do that until I ask 'Uthman ibn 'Affan." So she asked him about that, and he said: "As for me, I would not allow anyone to see them both at the same time."