Yahya related to me from Malik from Ibn Shihab from Qabisa ibn Dhu'ayb that a man asked Uthman ibn Affan whether one could have intercourse with two sisters who one owned. Uthman said, "One ayat makes them halal, and one ayat makes them haram. As for me, I wouldn't like to do it." The man left him and met one of the companions of the Messenger of Allah ﷺ and asked him about it, and he said, "Had I any authority and I found someone who had done it, I would punish him as an example." Ibn Shihab added, "I think that it was Ali ibn Abi Talib. "  

قَالَ فَخَرَجَ مِنْ عِنْدِهِ فَلَقِيَ رَجُلاً مِنْ أَصْحَابِ رَسُولِ اللَّهِ ﷺ فَسَأَلَهُ عَنْ ذَلِكَ فَقَالَ لَوْ كَانَ لِي مِنَ الأَمْرِ شَىْءٌ ثُمَّ وَجَدْتُ أَحَدًا فَعَلَ ذَلِكَ لَجَعَلْتُهُ نَكَالاً قَالَ ابْنُ شِهَابٍ أُرَاهُ عَلِيَّ بْنَ أَبِي طَالِبٍ  

"عَنِ الزُّهْرِىِّ، عَنْ قُبَيْصَةَ بْنِ ذُؤَيْب أَن عثمَانَ سُئلَ عَنِ الأخْتَيْنِ الأمَتَيْنِ منْ ملكِ اليَمِينِ، هَلْ يُجْمَعُ بَيْنَهُمَا؟ فَقَالَ: أحَلَّتهُمَا آيَةٌ وَحَرَّمَتْهمَا آيَةٌ، وَمَا أُحِبُّ أَنْ أصْنَعَهُ، فَبَلَغَ ذَلِكَ رَجُلًا مِنْ أَصْحَابِ النبِىِّ ﷺ فَقَالَ: لَوْ وُلِّيتُ شَيْئًا مِنْ أُمُورِ المُسْلِمينَ ثُمَّ جِئْتُ بِهَذا جَعَلتُهُ نَكالا، قَالَ الزُّهْرِىُّ: أُرَاهُ عَلِيّا".