Abu Ma'bad says: Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) married his slave to (his) slave-woman, and he divorced her. Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: "Take her back," but he refused. The narrator says: Ibn Abbas (may Allah be pleased with them both) said: "She is yours; have intercourse with her by right of possession." He meant that she is lawful for him through marriage and that he has no power of divorce.
Imam al-Shafi'i (may Allah have mercy on him) says in his new view that Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said to his slave, who had divorced his wife: "You have no divorce; keep your wife." But he refused. The intent of Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) was that she is lawful for you through marriage, and there is no divorce for him.
The Shaykh (may Allah have mercy on him) said: It is as he said.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13856