Sahih Muslim Book 35, Hadith Number 6512.
Chapter : The merit of pronouncing Tablil, Tasbib and supplication.
Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: The uttering of (these words): “Hallowed be Allah; all praise is due to Allah, there is no god but Allah and Allah is the Greatest,” is dearer to me than anything over which the sun rises.