Musannaf Ibn Abi Shaybah

Hazrat Abu Maryam Thaqafi says that Hazrat Hasan bin Ali (may Allah be pleased with him) led us in the Maghrib prayer. When he completed the prayer, he performed two prostrations of forgetfulness, although we did not know what mistake he had made. When he finished with the salam, we asked him about it, saying, "Why did you do this?" He replied, "I made a mistake."