Musannaf Ibn Abi Shaybah 4600 — Those who prostrated for forgetfulness

Abu Maryam al-Thaqafi said: Sayyiduna al-Hasan bin Ali (may Allah be pleased with him) led us in the Maghrib prayer. When he had completed the prayer, he performed the two prostrations of forgetfulness, although we did not know what lapse he had made. When he had said the salam, we asked him about it: "Why did you do this?" He said: "I made a lapse."