Sahih Muslim Book 4, Hadith Number 784.

Chapter : The reciting of al-Fatiha in every Rakah of prayer is obligatory.

‘Imran b. Husain reported: The Messenger of Allah (may peace be upon him) observed the Zuhr prayer and a person recited Sabbih Isma Rabbik al-a’la (Glorify the name of thy Lord, the Most High) behind him. When he (the Holy Prophet) concluded the prayer he said: Who amongst you recited (the above-mentioned verse) or who amongst you was the reciter? A person said: It was I. Upon this he (the Holy Prophet) observed: I thought as if someone amongst you was disputing with me (in what I was reciting).