Musannaf Ibn Abi Shayba 19:376

Abu Bakr narrated to us, he said: Hafs narrated to us, from Dawud, from Sa’id ibn al-Musayyib, regarding the one who performs *li’an* (mutual cursing): If he declares himself a liar, he said: He is to be lashed, and he is a suitor (i.e., he is permitted to remarry her).