It is narrated from Ibn Musayyib (may Allah have mercy on him) that Nafi', who had corresponded with Umm al-Mu'mineen Sayyidah Umm Salamah (may Allah be pleased with her), gave his free wife two divorces. Then he asked 'Uthman ibn 'Affan (may Allah be pleased with him) about the matter, so 'Uthman (may Allah be pleased with him) said to him that she has become unlawful for you.
Hadith Referenceمسند الإمام الشافعي / كتاب الطلاق / 1260
Hadith Takhrijصحيح: اخرجه البيهقي: 368/7 - 369 ـ وفي المعرفة السنن والآثار له (4483) ـ ومالك في الموطأ، الطلاق، باب ما جاء في طلاق العبد۔