Musnad Ahmad Hadith 16708

Ma'di bin Sulaiman says that once Mutair said to his son Shu'ayth bin Mutair, "How did I narrate that tradition to you?" Shu'ayth replied, "Father! You told me that at the place of Dhi Khushub, Dhul-Yadayn met you, and he told you that once the Prophet (peace be upon him) led the Zuhr or Asr prayer—most likely Asr—and ended the prayer after only two rak'ahs. The hasty people, seeing this, left the mosque saying that the prayer had been shortened. Meanwhile, the Prophet (peace be upon him) also stood up, and Abu Bakr and Umar followed behind him, when Dhul-Yadayn came from the front and said, 'O Messenger of Allah! Has the prayer been shortened or did you forget?' The Prophet (peace be upon him) said, 'Neither has the prayer been shortened nor did I forget.' Then the Prophet (peace be upon him) turned towards the two Shaykhs and said, 'What is Dhul-Yadayn saying?' Both replied, 'O Messenger of Allah! He is speaking the truth.' So the Prophet (peace be upon him) returned, and the people also returned, and he led two more rak'ahs, and after saying salam, performed the prostration of forgetfulness (sajda sahw)."