Muwatta Malik #209

Yahya related to me from Malik from Da'ud ibn al-Husayn that Abu Sufyan, the mawla of Ibn Abi Ahmad, said that he heard Abu Hurayra say, "The Messenger of Allah, may Allah bless him and grant him peace, prayed asr and said the taslim after two rakas. Dhu'l-Yadayn stood up and said, 'Has the prayer been shortened, Messenger of Allah, or have you forgotten?' The Messenger of Allah, may Allah bless him and grant him peace, stood up and completed what remained of the prayer, and then, remaining sitting after saying the taslim, he made two prostrations."