This statement is said by Muslims numerous times. During the call for prayer, during prayer, when they are happy, and wish to express their approval of what they hear, when they slaughter an animal, and when they want to praise a speaker, Muslims do say this expression of Allahu Akbar. Actually it is most said expression in the world. Its meaning: "Allah is the Greatest." Muslims praise Allah in every aspect of life; and as such they say Allahu Akbar.