Musnad Ahmad 30:258

Sufyan narrated to us: Ayyub heard Muhammad ibn Sirin saying: I heard Abu Hurairah saying: The Messenger of Allah (ﷺ) prayed one of the two afternoon prayers, either Dhuhr or Asr—and my strongest suspicion is that it was Asr—and he performed the taslim after two rak'ahs. Then he went to a trunk that he used to pray towards and sat by it, angry. Sufyan said once: Then he went to a trunk in the qiblah that he used to lean his back against, and he leaned his back against it. He said: Then the hasty ones among the people left, and they said: "The prayer has been shortened." Among the people were Abu Bakr and Umar, and they were too awestruck to speak to him. Then Dhu al-Yadayn said: "O Messenger of Allah, has the prayer been shortened, or have you forgotten?" He said: "The prayer has not been shortened, and I have not forgotten." He said: "Indeed, you only prayed two rak'ahs." He said: So the Messenger of Allah (ﷺ) looked [at the people], and they said: "Yes." So he stood up and prayed two rak'ahs, then performed the taslim. Then he said the takbir and prostrated like his [usual] prostration or longer, then he raised his head and said the takbir, then he prostrated and said the takbir.