Al-Zuhri, Al-Nakha'i, Malik, Al-Layth, Al-Shafi'i, Ishaq, and Abu Thawr. Abu Hanifah said: If he remembers before he prostrates, he sits for the tashahhud. If he remembers after the prostration, and he had sat immediately after the fourth [rak'ah] for the duration of the tashahhud, his prayer is valid, and he adds another [rak'ah] to the excess so that it becomes a supererogatory prayer (nafilah). If he had not sat during the fourth, his obligatory prayer is rendered void, his prayer becomes a supererogatory prayer, and he must repeat the prayer. Hammad ibn Abi Sulayman said something similar. Qatadah and Al-Awza'i said regarding one who prayed Maghrib as four [rak'ahs]: He adds another to it, and the two [additional] rak'ahs become voluntary, because of the statement of the Prophet (peace and blessings of Allah be upon him) in the hadith of Abu Sa'id regarding one who prostrates twice: "If his prayer was complete, then the rak'ah and the two prostrations are a supererogatory act." Recorded by Abu Dawud and Ibn Majah (66). In another narration: "If he prayed five, they [the two prostrations] will balance his prayer for him." Recorded by Muslim (66). Our evidence is what Abdullah ibn Mas'ud narrated, saying: The Messenger of Allah (peace and blessings of Allah be upon him) led us in prayer and performed five [rak'ahs]. When he turned away, the people whispered among themselves, so he said: "What is the matter with you?" They said: O Messenger of Allah, has the prayer been increased? He said: "No." They said: But you prayed five. So he turned away, then prostrated twice, then performed the taslim, then said: "I am only a human being; I forget just as you forget. So if one of you forgets, let him prostrate twice." In another narration, he said: "I am only a human being like you; I remember as you remember, and I forget as you forget." Then he prostrated the two prostrations of forgetfulness. In another narration, he said: "So if a man increases or decreases, let him prostrate twice." [All of it was recorded] (67) by Muslim (68). It is apparent that the Prophet (peace and blessings of Allah be upon him) did not sit after the fourth [rak'ah], because it was not reported, and because he stood up to the fifth believing that he had stood up from the third, and his prayer was not rendered void by this, nor did he add another to the fifth.