Musannaf Ibn Abi Shayba 19:381

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Ibn Shubruma, from al-Harith; and from Sufyan, from Ibn Jurayj, from ‘Ata’; and from Sufyan, from Jabir, from al-Sha’bi, regarding the one who performs li’an (mutual imprecation) and then calls himself a liar: They said: He is to be lashed.