Sahih Muslim Book 4, Hadith Number 981.

Chapter : Following the Imam and acting after him.

‘Aisha reported: The Messenger of Allah (may peace be upon him’) often said while bowing and prostrating himself: “Glory be to Thee, O Allah, our Lord, and praise be to Thee, O Allah, forgive me,” thus complying with the (command in) the Qur’an.