Musannaf Ibn Abi Shayba 19:783

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Isma’il bin Abi Khalid, from al-Sha’bi, regarding a man who accused [his wife] of adultery (qadhf) then divorced her three times. He said: He performs li’an (imprecation) with her as long as she is in the waiting period (‘iddah).