Imam al-Zuhri (may Allah have mercy on him) narrates from Sayyiduna Sahl bin Sa'd (may Allah be pleased with him): I was present with the two who performed li'an in the time of the Messenger of Allah (peace and blessings be upon him), and they were separated. He said: "O Messenger of Allah (peace and blessings be upon him)! If I keep her as my wife, then I have lied against her."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللعان / 15323