The Messenger of Allah ﷺ prayed Dhuhr as five rakahs. He was asked, "Has the prayer been increased?"He replied, "What do you mean?"They said, "You prayed five rakahs."So he performed two prostrations after he had given the salam.
أن رسول الله ﷺ صلى الظهر خمسا، فقيل له: أزيد في الصلاة؟ فقال: ما ذاك؟ قال: صليت خمسا. فسجد سجدتين بعد ما سلم.
Bukhari related it in the Chapter on Forgetfulness (1226), and Muslim in the Chapter on Mosques (91, small number), both from the hadith of Shuba, from Hakam, from Ibrahim, from Alqama, from Abdullah bin Masud, who mentioned the same, and their wording is identical.The two sheikhs also related it, Bukhari in the Chapter on Prayer (401), and Muslim, both from the hadith of Jareer, from Mansur, from Ibrahim, with this wording, "So he folded his legs, faced the qibla, and performed two prostrations, then said the salam. When he turned his face toward us, he said, 'If something new had happened in the prayer, I would have informed you of it, but I am only a human being like you, I forget just as you forget, so if I forget, remind me. And if any of you is in doubt about his prayer, let him seek what is correct, complete his prayer accordingly, then say the salam, then perform two prostrations.'"In a version recorded by Muslim (95), from Hafs and Abu Muawiya, from Amash, from Ibrahim, with this wording, "The Prophet ﷺ performed the two prostrations of forgetfulness after the salam and after speaking."Tirmidhi said, "This is the practice followed by some scholars, who say, if a man prays Dhuhr with five rakat, his prayer is valid, and he performs the two prostrations of forgetfulness, even if he did not sit after the fourth rakat. This is the view of Shafii, Ahmad, and Ishaq. Others said, if he prays Dhuhr with five rakat and did not sit after the fourth rakat for the duration of the tashahhud, his prayer is invalidated. This is the view of Sufyan Thawri and some scholars of Kufa." Tirmidhi (2/239).Khattabi said, "Abu Hanifa said, if he did not sit after the fourth rakat for the duration of the tashahhud, and prostrated in the fifth, his prayer is invalid, and he must start the prayer over. But if he did sit after the fourth rakat for the duration of the tashahhud, then his Dhuhr prayer is complete, and the fifth rakat is a voluntary one, so he must add another rakat to it, then say the tashahhud and the salam, and perform the two prostrations of forgetfulness, and his prayer is complete." He said, "Following the sunnah is preferable, and the chain of this hadith is as sound as can be among the chains of the scholars of Kufa."As for what is related from Thawban, from the Prophet ﷺ, who said, "For every instance of forgetfulness there are two prostrations after the salam," this is daif. The Hafiz declared it daif in Bulugh Maram, and Bayhaqi, Ibn Jawzi, Abdul-Haqq, and others had already declared it so before him.I say, Abu Dawud related it (1038), saying, Amr bin Uthman, Rabi bin Nafi, Uthman bin Abu Shayba, and Shuja bin Makhlad narrated to us, with the same meaning in the chain, that Ibn Ayyash related to them from Ubaydullah bin Ubayd Kalai, from Zuhayr, meaning Ibn Salim Ansi, from Abdul-Rahman bin Jubayr bin Nufayr. Amr alone added, from his father, from Thawban, mentioning the same.Ibn Majah related it (1219) from Hisham bin Ammar and Uthman bin Abu Shayba, who both said, Ismail bin Ayyash narrated to us with the same wording.Zuhayr bin Salim Ansi was not deemed reliable by anyone except Ibn Hibban. Daraqutni said, "A man of Homs, of unreliable hadith, he narrated from Thawban but never heard directly from him."Bayhaqi said (2/337), "This chain contains weakness, and the hadith of Abu Hurairah and Imran and others about multiple instances of forgetfulness occurring together from the Prophet ﷺ, with the Prophet limiting himself to just two prostrations, contradicts this." This means that the two prostrations of forgetfulness are meant to be repeated according to how many times forgetfulness occurs, whereas the hadith of Abu Hurairah and Imran indicates that only two prostrations of forgetfulness are performed even if the forgetfulness is repeated multiple times. It has also become clear that the two prostrations of forgetfulness may, in some cases, occur before the salam.The hadith has other chains recorded by Tabarani and others, but they are weaker than this one.Likewise, what is related from Ayesha, who said, the Messenger of Allah ﷺ said, "The two prostrations of forgetfulness are for every addition and omission," is daif. Bazzar related it in Kashf Astar (574), saying, Humayd bin Rabi narrated to us, Muhammad bin Bakkar narrated to us, Hakeem bin Nafi narrated to us, from Hisham, from his father, from Ayesha, who mentioned the hadith with the same wording.Abu Yaala related it in Maqsad Ali (321) from Ismail bin Ibrahim, Hakeem bin Nafi narrated to us with the same wording.Hakeem bin Nafi is the one from Raqqa. Abu Zura said of him, "He is of no value," while Ibn Main deemed him reliable. It has also been reported that he was described as unreliable.This hadith was also recorded by Ibn Adi in Kamil (2/639) from Ahmad bin Mansur Hasib and Ali bin Saeed Razi, who both said, Muhammad bin Bakkar narrated to us. He also said, Hamd bin Hafs narrated to us, who said, Tarjumani narrated to us, both saying, Hakeem bin Nafi narrated to us with the same chain, with the wording, "Two prostrations suffice for every addition and omission." Hasib and Ali did not include the word "suffice."Ibn Adi said, "I do not know of anyone who related this hadith from Hisham bin Urwa other than Hakeem bin Nafi. It has also been related from Abu Jafar Razi, from Hisham bin Urwa, and it is said that Abu Jafar is in fact the kunya of Hakeem bin Nafi, so it seems the hadith comes back to the fact that no one related it from Hisham except Hakeem." End of quote.Dhahabi said in Mizan (1/586), "Ibn Adi recorded from him hadiths that are not extremely problematic, and it has been reported from Ibn Main that he described him as unreliable." This is an indication that the hadith is to be judged daif, and the hadith has other chains weaker than these.