Thabit al-A'raj said: I married the umm walad (slave-mother) of Abd al-Rahman bin Zayd bin al-Khattab. His son summoned me and also summoned two of his slaves. They tied me up, beat me with whips and said: "Divorce her, or we will surely do such-and-such." He said: I divorced her. Then I asked Ibn Umar and Ibn al-Zubayr (may Allah be pleased with them both), and they did not count it as a divorce.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 15106