Regarding The Sunnah For Divorcing Slaves Sunan Abi Dawud 2187

Arabic hadith text
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، حَدَّثَنَا عَلِيُّ بْنُ الْمُبَارَكِ، حَدَّثَنِي يَحْيَى بْنُ أَبِي كَثِيرٍ، أَنَّ عُمَرَ بْنَ مُعَتِّبٍ، أَخْبَرَهُ أَنَّ أَبَا حَسَنٍ مَوْلَى بَنِي نَوْفَلٍ أَخْبَرَهُ أَنَّهُ، اسْتَفْتَى ابْنَ عَبَّاسٍ فِي مَمْلُوكٍ كَانَتْ تَحْتَهُ مَمْلُوكَةٌ فَطَلَّقَهَا تَطْلِيقَتَيْنِ ثُمَّ عَتَقَا بَعْدَ ذَلِكَ هَلْيَصْلُحُ لَهُ أَنْ يَخْطُبَهَا قَالَ نَعَمْ قَضَى بِذَلِكَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏
Translation
Narrated Umar ibn Mu'tab

Abu Hasan, the freed slave of the Banu Nawfal, asked Ibn Abbas about a slave who was married to a slave-girl: He divorced her twice, and then they were freed after that. Is it permissible for him to propose to her? He said: Yes, the Messenger of Allah, peace and blessing be upon him, ruled accordingly.