[Machine] In a man who commits adultery with his mother-in-law or his daughter-in-law, they both become unlawful for him to marry and their marriage is annulled. Yahya bin Ya'mar said, "Nothing is ever forbidden that was not permissible at some point." When the statement reached Sha'bi, he said, "If you were to take a cup of wine and pour it into a container of water, that water would become forbidden." It was the opinion of Sha'bi that such a combination was forbidden for him.  

فِي رَجُلٍ زَنَى بِأُمِّ امْرَأَتِهِ أَوْ بِابْنَتِهَا فَإِنَّهُمَا حُرْمَتَانِ تَخَطَّاهُمَا وَلَا يُحَرِّمُهَا ذَلِكَ عَلَيْهِ قَالَ وَقَالَ يَحْيَى بْنُ يَعْمَرَ مَا حَرَّمَ حَرَامٌ حَلَالًا قَطُّ فَبَلَغَ ذَلِكَ الشَّعْبِيَّ فَقَالَ بَلْ لَوْ أَخَذْتَ كُوزًا مِنْ خَمْرٍ فَسَكَبْتَهُ فِي جُبٍّ مِنْ مَاءٍ لَكَانَ ذَلِكَ الْمَاءُ حَرَامًا وَكَانَ مِنْ رَأْيِ الشَّعْبِيِّ أَنَّهَا قَدْ حُرِّمَتْ عَلَيْهِ