Musnad Ahmad 1013:35

Ibn Idris narrated to us, Ibn Ishaq narrated to us, from al-Zuhri, from Sahl ibn Sa’d al-Sa’idi, who said: When ‘Uwaymir, the brother of the Banu al-‘Ajlan, performed the *li’an* (oath of imprecation) with his wife, he said: "O Messenger of Allah, I have wronged her if I keep her. She is divorced. She is divorced. She is divorced."