The Imam Is To Be Followed

[Quran 15:98]
So glorify the praises of your Lord and be of those who prostrate themselves (to Him).

[Bukhari 1:11:656]
Narrated Aisha: The mother of the believers: Allah's Apostle during his illness prayed at his house while sitting whereas some people prayed behind him standing. The Prophet beckoned them to sit down. On completion of the prayer, he said,

'The Imam is to be followed: bow when he bows, raise up your heads (stand erect) when he raises his head and when he says, 'Sami a-l-lahu liman-hamida ' (Allah heard those who sent praises to Him) say then 'Rabbana wa laka-l-hamd' (O our Lord! All the praises are for You), and if he prays sitting then pray sitting."

[Muslim 4:759]
Ibn Umar reported that the Messenger of Allah (may peace be upon him), when he stood up for prayer, used to raise his hands apposite the shoulders and then recited takbir (Allah-o-Akbar),
and when he was about to bow he again did like it and when he raised himself from the ruku' (bowing posture) he again did like it, but he did not do it at the time of raising his head from prostration.