From the Arabic root sha-hi-da, lit. the act of bearing witness or the public declaration of belief. It is among the key principles of Islam. The shahada has two parts: the first attests that ‘there is no god but God’; the second attests that ‘Muhammad is Messenger of Allah’ It is the second part that distinguishes Muslims from the followers of other monotheistic religions. When pronouncing the shahada, Shi‘i Muslims often add the affirmation of Imam ‘Ali as the Imam of the faithful (amir al-mu’nin).