Musannaf Ibn Abi Shayba 19:137

Abu Bakr narrated to us, he said: Yahya bin Abd al-Malik bin Abi Ghaniyah narrated to us, from his father, from al-Hakam, he said: If a man accuses a man [of adultery], and he has a Jewish or Christian mother, then there is no prescribed punishment (hadd) upon him.