Musannaf Ibn Abi Shayba 35:81

Ibn ‘Uyaynah narrated to us, from al-Zuhri, who heard Sahl ibn Sa‘d: He witnessed the two who performed *li‘an* (mutual cursing) during the time of the Prophet, may Allah bless him and grant him peace. He (the Prophet) separated them. He (the man) said, "O Messenger of Allah, I have lied against her if I keep her."