Hadith 1939
Sayyiduna Abdullah bin Buhaina Asadi (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) stood up during the Zuhr prayer at the point when he was supposed to sit. When he completed the prayer, before saying the salam, he performed two prostrations while sitting. The people also performed these two prostrations. These were in place of the sitting that he had forgotten.