Musnad Ahmad 27:502

Abdullah ibn Ahmad said: My father said, and he narrated to us before him, he said: Hisham and Ibn 'Awn narrated to us, from Muhammad, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) led us in one of the two afternoon prayers, praying two rak'ahs, then he performed the taslim. Then he mentioned the hadith, so he should answer.