Regarding The Sunnah For Divorcing Slaves Sunan Abi Dawud 2188

Arabic hadith text
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عُثْمَانُ بْنُ عُمَرَ، أَخْبَرَنَا عَلِيٌّ، بِإِسْنَادِهِ وَمَعْنَاهُ بِلاَ إِخْبَارٍ قَالَ ابْنُ عَبَّاسٍ بَقِيَتْ لَكَ وَاحِدَةٌ قَضَى بِهِ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏ قَالَ أَبُو دَاوُدَ سَمِعْتُ أَحْمَدَ بْنَ حَنْبَلٍ قَالَ قَالَ عَبْدُ الرَّزَّاقِ قَالَ ابْنُ الْمُبَارَكِ لِمَعْمَرٍ مَنْ أَبُو الْحَسَنِ هَذَا لَقَدْ تَحَمَّلَ صَخْرَةً عَظِيمَةً ‏.‏ قَالَ أَبُو دَاوُدَ أَبُو الْحَسَنِ هَذَا رَوَى عَنْهُ الزُّهْرِيُّ قَالَ الزُّهْرِيُّ وَكَانَ مِنَ الْفُقَهَاءِ رَوَى الزُّهْرِيُّ عَنْ أَبِي الْحَسَنِ أَحَادِيثَ ‏.‏ قَالَ أَبُو دَاوُدَ أَبُو الْحَسَنِ مَعْرُوفٌ وَلَيْسَ الْعَمَلُ عَلَى هَذَا الْحَدِيثِ
Translation
The aforesaid tradition (No. 2182) has also been transmitted by Ali (ibn al-Mubarak) through a different chain of narrators to the same effect. This version adds

Ibn Abbas said: "There remains for you one [oath or ruling], which the Messenger of Allah, may Allah bless him and grant him peace, judged by."

Abu Dawud said: I heard Ahmad b. Hanbal say: 'Abd al-Razzaq said that Ibn al-Mubarak said to Ma'mar: "Who is this Abu al-Hasan? He has taken upon himself a grave matter."

Abu Dawud said: Al-Zuhri narrated from him. Al-Zuhri said: "He was among the jurists." Al-Zuhri narrated many traditions from Abu al-Hasan.

Abu Dawud said: Abu al-Hasan is well-known, and the practice is not based upon this hadith.