Ahmad ibn Muhammad from al-Hasan ibn Mahbub from Jamil from Sama’ah from Abu Abdillah عليه السلام, peace be upon him: Imam al-Sadiq عليه السلام was asked regarding a man whom the imam (of prayer) precedes by one rak‘ah, and the imam (of prayer) makes a mistake and prays five rak‘ahs. Imam عليه السلام said: “He should repeat that rak‘ah and should not consider the mistake of the imam (of prayer).”