Musannaf Ibn Abi Shayba 19:438

Abu Bakr narrated to us, he said: Yazid bin Harun narrated to us, he said: Sufyan bin Husayn narrated to us, from Abu Ali al-Rahbi, from Ikrimah, who said: Al-Hasan bin Ali was asked about a man who came upon an animal. He said: "If he is a *muhsan* (a person who has previously engaged in lawful sexual intercourse), he is to be stoned."