Musannaf Ibn Abi Shayba 3:1952

'Abbad ibn al-'Awwam narrated to us, from Sufyan ibn Husayn, who said: I heard al-Hasan, and he recited the prostration that is in [Surah] Sad, then he prostrated on the edge of a pillar. Then he said to the people: "Turn [towards the Qibla]."