Musnad Ahmad 830:97

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Qatadah, from al-Hasan, that Abu Bakrah entered the mosque while the Imam was bowing, so he bowed before reaching the row. The Prophet, peace and blessings of Allah be upon him, said to him: "May Allah increase you in eagerness, and do not do it again."