Musnad Abu Ya'la al-Mawsili 111:111

Zuhayr narrated to us, Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Ishaq, who said: Talha ibn Nafi' mentioned from Sa'id, from Abdullah ibn Abbas, who said: A man from the Ansar married a woman from the Banu 'Ajlan. He consummated the marriage with her and spent the night with her. When he woke up, he said, "I did not find her a virgin." Her matter was raised to the Messenger of Allah (peace be upon him). He summoned the young woman and asked her, and she said, "Nay, I was indeed a virgin." He said: So the Messenger of Allah (peace be upon him) ordered them to perform *li'an* (mutual imprecation), and he gave her the dowry.