Ibn Abbas was asked about a slave who divorced his wife with two pronouncements of divorce and then both were freed, could he remarry her? He said, "Yes."He was asked, "On whose authority?"He replied, "The Messenger of Allah ﷺ ruled that way."Abdul-Razzaq said that Abdullah bin Mubarak remarked, "Abu al-Hasan has shouldered a massive boulder on his neck with this."
حدثنا محمد بن عبد الملك بن زنجويه أبو بكر حدثنا عبد الرزاق حدثنا معمر عن يحيى بن أبي كثير عن عمر بن معتب
سئل ابن عباس عن عبد طلق امرأته تطليقتين ثم أعتقا يتزوجها قال نعم فقيل له عمن قال قضى بذلك رسول الله ﷺ قال عبد الرزاق قال عبد الله بن المبارك لقد تحمل أبو الحسن هذا صخرة عظيمة على عنقه
[Its chain of transmission is daif] Reported by Abu Dawud in "Divorce," chapter on the manner of a slave's divorce, hadith no. 2187, from the hadith of Yahya, with this wording.Umar bin Muattib is daif, as stated in Taqrib and elsewhere. The chain indicates that Yahya bin Abu Kathir also used to narrate from weak narrators.