Musannaf Ibn Abi Shayba 19:389

Abu Bakr narrated to us, he said: Hafs narrated to us, from Ash'ath, from al-Hakam, from Ibrahim, who said: "If a person who has been flogged (for slander) accuses his wife (of adultery), he is to be flogged, and there is no *li'an* (imprecation) between them." He said: And I asked al-Hasan and 'Amir, and they both said: "He performs *li'an*."