There is no god worthy of worship except God and Muhammad (peace be upon Him) is His messenger
This declaration of faith is called the Shahada, a simple formula which all the faithful pronounce. In Arabic, the first part is la ilaha illa Allah - "there is no god except God"; ilaha (god) can refer to anything which we may be tempted to put in place of God -- wealth, power, and the like. Then comes illa Allah:" except God, the source of all creation. The second part of the Shahada is Muhammadun rasulu Allah: "Muhammad (peace be upon Him) is the messenger of God". A message of guidance has come through a man like ourselves.
la ilaha illa Allah, Muhammadun rasulu Allah