Sahih Muslim Book 4, Hadith Number 788.

Chapter : The one led in prayer is forbidden to recite loudly behind the Imam.

‘Abda reported: ‘Umar b. al-Khattab used to recite loudly these words: Subhanak Allahumma wa bi hamdika wa tabarakasmuka wa ta’ala jadduka wa la ilaha ghairuka [Glory to Thee, O Allah, and Thine is the Praise, and Blessed is Thy name and Exalted is Thy Majesty and there is no other object of worship beside Thee]. Qatada informed in writing that Anas b. Malik had narrated to him: I observed prayer behind the Apostle of Allah (may peace be upon him) and Abu Bakr and Umar and ‘Uthman. They started (loud recitation) with: AI-hamdu lillahi Rabb al-‘A1amin [All Praise is due to Allah, the Lord of the worlds] and did not recite Bismillah ir-Rahman-ir-Rahim (loudly) at the beginning of the recitation or at the end of it.