Musannaf Ibn Abi Shayba 19:893

Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from Ash'ath, from al-Hasan, that Abu Bakr said regarding a man who says to a man, "O wicked one, O corrupt one": He said: He has spoken a bad word, but there is no punishment or prescribed legal penalty (hadd) in it.