ذِكْرُ إِبَاحَةِ جَمْعِ الْمَرْءِ بَيْنَ السُّورَتَيْنِ فِي الرَّكْعَةِ الْوَاحِدَةِ
"I heard Abu Wa'il say: "A man said in the presence of Abdullah: 'I recited Al-Mufassal in one rak'ah.' He said: 'That is like reciting poetry. I know the similar surahs that the Messenger of Allah ﷺ used to recite together.' And he mentioned twenty surahs from Al-Mufassal, two by two in each rak'ah." (Using translation from Nasāʾī 1005)
إِنِّي قَرَأْتُ الْمُفَصَّلَ اللَّيْلَةَ كُلَّهُ فِي رَكْعَةٍ فَقَالَ عَبْدُ اللَّهِ «هَذَا كَهَذِّ الشِّعْرِ لَقَدْ عَرَفْنَا النَّظَائِرَ الَّتِي كَانَ رَسُولُ اللَّهِ ﷺ يَقْرِنُ بِهِنَّ فَذَكَرَ عِشْرِينَ سُورَةً مِنَ الْمُفَصَّلِ سُورَتَيْنِ سُورَتَيْنِ فِي رَكْعَةٍ»