Musannaf Ibn Abi Shayba 19:816

Abu Bakr narrated to us, he said: Ibn Mahdi narrated to us, from Sufyan, from Sa'id al-Zubaydi, from Hammad, from Ibrahim, regarding a man who says to a man, "You are not your father's son," and "Your mother is a Jewish or Christian slave woman." He said: There is no prescribed punishment (hadd) upon him.