Sahih Muslim Book 4, Hadith Number 771.

Chapter : The reciting of Takbir at the time of bowing and rising in prayer except rising after Ruku’ when it is said: Allah listened to him who praised Him.

‘Ubada b. as-Samit reported from the Apostle of Allah (may peace be upon him ): He who does not recite Fatihat al-Kitab is not credited with having observed the prayer.