Musnad Abu Ya'la al-Mawsili 3:293

Abu Musa narrated to us, Wahb ibn Jarir narrated to us, my father narrated to us, he said: I heard Yahya ibn Ayyub narrating from Yazid ibn Abi Habib, from Marthad, from Hassan ibn Kurayb, from Ali, that he used to say: The one who speaks the obscenity and the one who listens to it are equal in sin.