Musnad Ahmad 30:2668

Yazid narrated to us, he said: Muhammad—meaning Ibn Ishaq—informed us, from Sa'id ibn Abi Sa'id al-Maqburi, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) led us in the Dhuhr prayer, and there was a man in the back of the rows who performed his prayer poorly. When he (the Prophet) finished the prayer, the Messenger of Allah (ﷺ) called out to him: "O so-and-so, do you not fear Allah? Do you not see how you pray? You think that anything you do is hidden from me. By Allah, I see what is behind me just as I see what is in front of me."