Musnad Ahmad 830:84

'Affan narrated to us, Hammad ibn Salamah narrated to us, Ziyad al-A'lam informed us, from al-Hasan, from Abu Bakrah, that he arrived while the Messenger of Allah (peace and blessings of Allah be upon him) was bowing (in prayer), so he bowed before reaching the row, then he walked to the row. The Prophet (peace and blessings of Allah be upon him) said: "Who is this who bowed, then walked to the row?" Abu Bakrah said: "I am." The Prophet (peace and blessings of Allah be upon him) said: "May Allah increase you in eagerness, but do not do it again."