Musannaf Ibn Abi Shayba 19:390

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Ash'ath, from Mansur and Hammad, from Ibrahim, who said: If a man accuses his wife of adultery (qadhf) and he has already been flogged with the prescribed punishment (hadd), he is flogged [again], and he does not perform li'an (imprecation), because his testimony is not permissible.