The most important duty of every Muslim is the recitation of the creed, or profession of faith, in one version or another: There is no god but God, and Muhammad is his prophet. Muslims will also preface the profession with the words, I bear witness that… and favor the word messenger over the more westernized and Judeo-Christian idea of a prophet.
The profession of faith takes its origins from Muhammad’s destruction of all deities and idolatrous objects, including money and luxury, from the Arab pantheon except the “One True God.”
But the profession had an equally significant socio-political implication. Tribes were the most important unit of political and economic power in the Arab world of Muhammad’s time. To be a member of a given tribe, one had to be born into it, or, less likely, to marry into it. To become a member of the Islamic umma, or community, one only had to make the declaration of faith. It was a momentously consequential end-run around old strictures of power and convention, immediately giving Muhammad in particular and Muslims in general a means of increasing their numbers and powers rapidly while shattering old expectations and prejudices.