It was narrated that ‘Abdullah ibn Yazid said: al-Bara’ – who is not a liar – told me: When the Messenger of Allah (blessings and peace of Allah be upon him) said, “Sami‘a Allahu liman hamidah (Allah hears those who praise Him),” none of us would bend down [to prostrate] until the Prophet (blessings and peace of Allah be upon him) had prostrated fully, then we would prostrate after him..
Commentary : There are rules and regulations for offering the prayer in congregation, that the Muslim should pay attention to and learn. One of the most important of these rules is that the worshipper should follow the imam in all his movements, for the imam has been appointed to be followed. The Sahabah (may Allah be pleased with them) applied this rule when praying behind the Prophet (blessings and peace of Allah be upon him), as is described in this hadith, in which al-Bara’ ibn ‘Azib (may Allah be pleased with him) narrates that when the Prophet (blessings and peace of Allah be upon him) raised his head from bowing and said, “Sami‘a Allahu liman hamidah (Allah hears those who praise Him),” and those who were praying behind him stood up straight after bowing, they would remain standing, and none of them would bend down to prostrate or hasten to prostrate until the Prophet (blessings and peace of Allah be upon him) had prostrated fully, by placing his forehead on the ground. Then they would prostrate after him (blessings and peace of Allah be upon him)..