Musannaf Ibn Abi Shayba 19:815

Abu Bakr narrated to us, he said: Ibn Idris narrated to us, from his paternal uncle, from al-Sha'bi, that he was asked about a man who accused a man of adultery, while his (the accused's) mother was a polytheist. He said: "Do you see, if a man accused al-Ash'ath, would he not be lashed?"