Messengers of Allah have the most perfect reasons, the firmest hearts, and the best endurance, and they are the best in terms of fulfilling the rights of Allah, the Exalted. Yet, they never went beyond the limits of human nature. The Messenger of Allah (may Allah's peace and blessings be upon him) was the most perfect in all these characteristics.
However, he once forgot due to his human nature, so that Allah would legislate for His slaves the rulings regarding forgetfulness in prayer. Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) led his companions in Zhuhr or ‘Asr prayer. Abu Hurayrah actually defined this prayer, but the sub-narrator Ibn Sirīn forgot it.
When the Prophet (may Allah's peace and blessings be upon him) prayed the first two Rak‘ahs, he finished the prayer by making Taslīm. The Prophet (may Allah's peace and blessings be upon him) is a perfect man and feels contented only with the perfect work. Therefore, he felt there was a sort of deficiency or fault, but he did not know the source of such feeling.
So, he went toward a piece of wood lying across Qiblah of the mosque, leaned upon it, and interlaced his fingers.
Those who were in a haste left the mosque through its gates while discussing with one another that something had happened, which was that the prayer had been shortened. Perhaps they thought that forgetfulness could not occur to the one who is a Prophet.
The Prophet (may Allah's peace and blessings be upon him) was highly respected, and thus no one dared to discuss this crucial issue with him. Even Abu Bakr and ‘Umar (may Allah be pleased with both of them) did not dare to ask him particularly they had seen him in a state of anxiety and depression.
A man from the companions called Dhu al-Yadayn broke the silence by asking the Prophet (may Allah's peace and blessings be upon him): "O Messenger of Allah, have you forgotten or has the prayer been shortened?"
He did not could not assure any of the two probabilities since both were possible to take place at that time. he to the best of his thought said: "I neither forgot nor was it shortened." When Dhu al-Yadayn realized that the prayer had not been shortened, and he was certain that he prayed only two Rak‘ahs, he knew that the Prophet (may Allah's peace and blessings be upon him) had forgotten, so he said: "Rather, you have forgotten."
The Prophet (may Allah's peace and blessings be upon him) wanted to confirm the accuracy of Dhu al-Yadayn's claim, which contradicted his thought that his prayer was complete, so he sought someone to support his statement and asked his companions around him: "Is what Dhu al-Yadayn has said true – that I only prayed two Rak‘ahs?"
When they answered in the affirmative, the Prophet (may Allah's peace and blessings be upon him) stepped forward and prayed what he had missed of the prayer. After reciting Tashahhud, he made Taslīm then said: "Allah Akbar" while he was sitting, then prostrated as he normally did or longer.
Then he raised his head from prostration and said: "Allah Akbar," then he said it again and prostrated as he normally did or longer. Then he raised his head and said: "Allah Akbar" and ended the prayer by making Taslīm without saying Tashahhud.
Who passed it on, from Imam al-Bukhari back to the one who was there.