Musannaf Ibn Abi Shayba 3:5391

Ghundar narrated to us, from Shu'bah, from al-Hakam, who said: It reached me from a man from Banu Tamim that he entered upon al-Hasan ibn Ali while he was sitting in his place of prayer. He said: "There is no Muslim who prays the morning prayer, then sits in his place of prayer, except that it is a veil for him from the Fire."