Sunan an-Nasa'i 3428
It was narrated that Abu Al-Hasan, the freed slave of Banu Nawfal, said:
"Ibn 'Abbas was asked about a slave who divorced his wife twice, then they were set free; could he marry her? He said: 'Yes.' He said: 'From whom (did you hear that)?' He said: 'The Messenger of Allah issued a Fatwa to that effect.'"
 (One of the narrators) 'Abdur-Razzaq said: "Ibn Al-Mubarak said to Ma'mar: 'Which Al-Hasan is this? He has taken on a heavy burden.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ رَافِعٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَنْبَأَنَا مَعْمَرٌ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ عُمَرَ بْنِ مُعَتِّبٍ، عَنِ الْحَسَنِ، مَوْلَى بَنِي نَوْفَلٍ قَالَ سُئِلَ ابْنُ عَبَّاسٍ عَنْ عَبْدٍ طَلَّقَ، امْرَأَتَهُ تَطْلِيقَتَيْنِ ثُمَّ عُتِقَا أَيَتَزَوَّجُهَا قَالَ نَعَمْ ‏.‏ قَالَ عَمَّنْ قَالَ أَفْتَى بِذَلِكَ رَسُولُ اللَّهِ صلى الله عليه وسلم قَالَ عَبْدُ الرَّزَّاقِ قَالَ ابْنُ الْمُبَارَكِ لِمَعْمَرٍ الْحَسَنُ هَذَا مَنْ هُوَ لَقَدْ حَمَلَ صَخْرَةً عَظِيمَةً ‏.‏