Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) was asked about a slave whose master marries him off; it was asked: In whose hand is the divorce? He (peace and blessings be upon him) said: "In the hand of the one who holds the shin" (that is, the one who is in the marriage is the one entitled to divorce).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11750