Nafi' (may Allah have mercy on him) narrates that Ibn Umar (may Allah be pleased with them both) used to say that whoever gives his slave permission to marry, then the right of divorce belongs only to the slave; no one other than the slave has the right of divorce.
Hadith Referenceمسند الإمام الشافعي / كتاب الطلاق / 1257
Hadith Takhrijاسناده صحیح اخرجه البيهقي : 7/360 - وفى المعرفة السنن والآثار له (4480)۔ وعبدالرزاق (12968)۔ وابن أبي شيبة (18383) - ومالك فى الموطأ الطلاق، باب ما جاء في طلاق العبد۔