It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that a man prayed behind the Prophet (peace and blessings be upon him), and he began bowing before he (peace and blessings be upon him) bowed and raising his head before he (peace and blessings be upon him) raised his. When the Prophet (peace and blessings be upon him) had completed the prayer, he (peace and blessings be upon him) asked: "Who is the one who did this?" He said: O Messenger of Allah, it was me; I wanted to know whether you are aware of that or not. He (peace and blessings be upon him) said: "Beware of deficiency in the prayer: when the imam bows, then bow, and when he raises his head, then raise yours."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Abdullah bin Usm (may Allah have mercy on him) except Ayyub bin Jabir, and Qutaybah (bin Sa'id) (may Allah have mercy on him) is alone in narrating it."