Musannaf Ibn Abi Shayba 19:419

Abu Bakr narrated to us, he said: Muhammad ibn Abd Allah al-Ansari narrated to us, from Ash'ath, from al-Hasan, regarding a man who says to another man, "So-and-so informed me that you committed adultery." He said: There is no prescribed punishment (hadd) upon him, because he attributed it to someone else.